!From inet!cs.utexas.edu!cline Tue Oct 31 17:10:31 CST 1989 !Received: from mojave.cs.utexas.edu by cs.utexas.edu (5.59/1.44) ! id AA29509; Tue, 31 Oct 89 17:11:51 CST !Posted-Date: Tue, 31 Oct 89 17:10:31 CST !Message-Id: <8910312310.AA04442@mojave.cs.utexas.edu> !Received: by mojave.cs.utexas.edu (14.5/1.4-Client) ! id AA04442; Tue, 31 Oct 89 17:10:34 cst !Date: Tue, 31 Oct 89 17:10:31 CST !X-Mailer: Mail User's Shell (6.5 4/17/89) !From: cline@cs.utexas.edu (Alan Cline) !To: ehg@research.att.com !Subject: New FITPACK Subset for netlib !This new version of FITPACK distributed by netlib is about 20% of !the total package in terms of characters, lines of code, and num- !ber of subprograms. However, these 25 subprograms represent about !95% of usages of the package. What has been omitted are such ca- !pabilities as: ! 1. Automatic tension determination, ! 2. Derivatives, arclengths, and enclosed areas for planar ! curves, ! 3. Three dimensional curves, ! 4. Special surface fitting using equispacing assumptions, ! 5. Surface fitting in annular, wedge, polar, toroidal, lunar, ! and spherical geometries, ! 6. B-splines in tension generation and usage, ! 7. General surface fitting in three dimensional space. !(The code previously circulated in netlib is less than 10% of the !total package and is more than a decade old. Its usage is dis- !couraged.) !Please note: Two versions of the subroutine snhcsh are included. !Both serve the same purpose: obtaining approximations to certain !hyperbolic trigonometric-like functions. The first is less accu- !rate (but more efficient) than the second. Installers should se- !lect the one with the precision they desire. !Interested parties can obtain the entire package on disk or tape !from Pleasant Valley Software, 8603 Altus Cove, Austin TX (USA), !78759 at a cost of $495 US. A 340 page manual is available for ! $30 US per copy. The package includes examples and machine !readable documentation. subroutine curv1 (n,x,y,slp1,slpn,islpsw,yp,temp, * sigma,ierr) c integer n,islpsw,ierr real x(n),y(n),slp1,slpn,yp(n),temp(n),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine determines the parameters necessary to c compute an interpolatory spline under tension through c a sequence of functional values. the slopes at the two c ends of the curve may be specified or omitted. for actual c computation of points on the curve it is necessary to call c the function curv2. c c on input-- c c n is the number of values to be interpolated (n.ge.2). c c x is an array of the n increasing abscissae of the c functional values. c c y is an array of the n ordinates of the values, (i. e. c y(k) is the functional value corresponding to x(k) ). c c slp1 and slpn contain the desired values for the first c derivative of the curve at x(1) and x(n), respectively. c the user may omit values for either or both of these c parameters and signal this with islpsw. c c islpsw contains a switch indicating which slope data c should be used and which should be estimated by this c subroutine, c = 0 if slp1 and slpn are to be used, c = 1 if slp1 is to be used but not slpn, c = 2 if slpn is to be used but not slp1, c = 3 if both slp1 and slpn are to be estimated c internally. c c yp is an array of length at least n. c c temp is an array of length at least n which is used for c scratch storage. c c and c c sigma contains the tension factor. this value indicates c the curviness desired. if abs(sigma) is nearly zero c (e.g. .001) the resulting curve is approximately a c cubic spline. if abs(sigma) is large (e.g. 50.) the c resulting curve is nearly a polygonal line. if sigma c equals zero a cubic spline results. a standard value c for sigma is approximately 1. in absolute value. c c on output-- c c yp contains the values of the second derivative of the c curve at the given nodes. c c ierr contains an error flag, c = 0 for normal return, c = 1 if n is less than 2, c = 2 if x-values are not strictly increasing. c c and c c n, x, y, slp1, slpn, islpsw and sigma are unaltered. c c this subroutine references package modules ceez, terms, c and snhcsh. c c----------------------------------------------------------- c nm1 = n-1 np1 = n+1 ierr = 0 if (n .le. 1) go to 8 if (x(n) .le. x(1)) go to 9 c c denormalize tension factor c sigmap = abs(sigma)*float(n-1)/(x(n)-x(1)) c c approximate end slopes c if (islpsw .ge. 2) go to 1 slpp1 = slp1 go to 2 1 delx1 = x(2)-x(1) delx2 = delx1+delx1 if (n .gt. 2) delx2 = x(3)-x(1) if (delx1 .le. 0. .or. delx2 .le. delx1) go to 9 call ceez (delx1,delx2,sigmap,c1,c2,c3,n) slpp1 = c1*y(1)+c2*y(2) if (n .gt. 2) slpp1 = slpp1+c3*y(3) 2 if (islpsw .eq. 1 .or. islpsw .eq. 3) go to 3 slppn = slpn go to 4 3 delxn = x(n)-x(nm1) delxnm = delxn+delxn if (n .gt. 2) delxnm = x(n)-x(n-2) if (delxn .le. 0. .or. delxnm .le. delxn) go to 9 call ceez (-delxn,-delxnm,sigmap,c1,c2,c3,n) slppn = c1*y(n)+c2*y(nm1) if (n .gt. 2) slppn = slppn+c3*y(n-2) c c set up right hand side and tridiagonal system for yp and c perform forward elimination c 4 delx1 = x(2)-x(1) if (delx1 .le. 0.) go to 9 dx1 = (y(2)-y(1))/delx1 call terms (diag1,sdiag1,sigmap,delx1) yp(1) = (dx1-slpp1)/diag1 temp(1) = sdiag1/diag1 if (n .eq. 2) go to 6 do 5 i = 2,nm1 delx2 = x(i+1)-x(i) if (delx2 .le. 0.) go to 9 dx2 = (y(i+1)-y(i))/delx2 call terms (diag2,sdiag2,sigmap,delx2) diag = diag1+diag2-sdiag1*temp(i-1) yp(i) = (dx2-dx1-sdiag1*yp(i-1))/diag temp(i) = sdiag2/diag dx1 = dx2 diag1 = diag2 5 sdiag1 = sdiag2 6 diag = diag1-sdiag1*temp(nm1) yp(n) = (slppn-dx1-sdiag1*yp(nm1))/diag c c perform back substitution c do 7 i = 2,n ibak = np1-i 7 yp(ibak) = yp(ibak)-temp(ibak)*yp(ibak+1) return c c too few points c 8 ierr = 1 return c c x-values not strictly increasing c 9 ierr = 2 return end subroutine curvs (n,x,y,d,isw,s,eps,ys,ysp,sigma,temp, * ierr) c integer n,isw,ierr real x(n),y(n),d(n),s,eps,ys(n),ysp(n),sigma,temp(n,9) c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine determines the parameters necessary to c compute a smoothing spline under tension. for a given c increasing sequence of abscissae (x(i)), i = 1,..., n and c associated ordinates (y(i)), i = 1,..., n, the function c determined minimizes the summation from i = 1 to n-1 of c the square of the second derivative of f plus sigma c squared times the difference of the first derivative of f c and (f(x(i+1))-f(x(i)))/(x(i+1)-x(i)) squared, over all c functions f with two continuous derivatives such that the c summation of the square of (f(x(i))-y(i))/d(i) is less c than or equal to a given constant s, where (d(i)), i = 1, c ..., n are a given set of observation weights. the c function determined is a spline under tension with third c derivative discontinuities at (x(i)), i = 2,..., n-1. for c actual computation of points on the curve it is necessary c to call the function curv2. the determination of the curve c is performed by subroutine curvss, the subroutine curvs c only decomposes the workspace for curvss. c c on input-- c c n is the number of values to be smoothed (n.ge.2). c c x is an array of the n increasing abscissae of the c values to be smoothed. c c y is an array of the n ordinates of the values to be c smoothed, (i. e. y(k) is the functional value c corresponding to x(k) ). c c d is a parameter containing the observation weights. c this may either be an array of length n or a scalar c (interpreted as a constant). the value of d c corresponding to the observation (x(k),y(k)) should c be an approximation to the standard deviation of error. c c isw contains a switch indicating whether the parameter c d is to be considered a vector or a scalar, c = 0 if d is an array of length n, c = 1 if d is a scalar. c c s contains the value controlling the smoothing. this c must be non-negative. for s equal to zero, the c subroutine does interpolation, larger values lead to c smoother funtions. if parameter d contains standard c deviation estimates, a reasonable value for s is c float(n). c c eps contains a tolerance on the relative precision to c which s is to be interpreted. this must be greater than c or equal to zero and less than or equal to one. a c reasonable value for eps is sqrt(2./float(n)). c c ys is an array of length at least n. c c ysp is an array of length at least n. c c sigma contains the tension factor. this value indicates c the degree to which the first derivative part of the c smoothing functional is emphasized. if sigma is nearly c zero (e. g. .001) the resulting curve is approximately a c cubic spline. if sigma is large (e. g. 50.) the c resulting curve is nearly a polygonal line. if sigma c equals zero a cubic spline results. a standard value for c sigma is approximately 1. c c and c c temp is an array of length at least 9*n which is used c for scratch storage. c c on output-- c c ys contains the smoothed ordinate values. c c ysp contains the values of the second derivative of the c smoothed curve at the given nodes. c c ierr contains an error flag, c = 0 for normal return, c = 1 if n is less than 2, c = 2 if s is negative, c = 3 if eps is negative or greater than one, c = 4 if x-values are not strictly increasing, c = 5 if a d-value is non-positive. c c and c c n, x, y, d, isw, s, eps, and sigma are unaltered. c c this subroutine references package modules curvss, terms, c and snhcsh. c c----------------------------------------------------------- c c decompose temp into nine arrays and call curvss c call curvss (n,x,y,d,isw,s,eps,ys,ysp,sigma,temp(1,1), * temp(1,2),temp(1,3),temp(1,4),temp(1,5), * temp(1,6),temp(1,7),temp(1,8),temp(1,9), * ierr) return end function curv2 (t,n,x,y,yp,sigma) c integer n real t,x(n),y(n),yp(n),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this function interpolates a curve at a given point c using a spline under tension. the subroutine curv1 should c be called earlier to determine certain necessary c parameters. c c on input-- c c t contains a real value to be mapped onto the interpo- c lating curve. c c n contains the number of points which were specified to c determine the curve. c c x and y are arrays containing the abscissae and c ordinates, respectively, of the specified points. c c yp is an array of second derivative values of the curve c at the nodes. c c and c c sigma contains the tension factor (its sign is ignored). c c the parameters n, x, y, yp, and sigma should be input c unaltered from the output of curv1. c c on output-- c c curv2 contains the interpolated value. c c none of the input parameters are altered. c c this function references package modules intrvl and c snhcsh. c c----------------------------------------------------------- c c determine interval c im1 = intrvl(t,x,n) i = im1+1 c c denormalize tension factor c sigmap = abs(sigma)*float(n-1)/(x(n)-x(1)) c c set up and perform interpolation c del1 = t-x(im1) del2 = x(i)-t dels = x(i)-x(im1) sum = (y(i)*del1+y(im1)*del2)/dels if (sigmap .ne. 0.) go to 1 curv2 = sum-del1*del2*(yp(i)*(del1+dels)+yp(im1)* * (del2+dels))/(6.*dels) return 1 sigdel = sigmap*dels call snhcsh (ss,dummy,sigdel,-1) call snhcsh (s1,dummy,sigmap*del1,-1) call snhcsh (s2,dummy,sigmap*del2,-1) curv2 = sum+(yp(i)*del1*(s1-ss)+yp(im1)*del2*(s2-ss))/ * (sigdel*sigmap*(1.+ss)) return end function curvd (t,n,x,y,yp,sigma) c integer n real t,x(n),y(n),yp(n),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this function differentiates a curve at a given point c using a spline under tension. the subroutine curv1 should c be called earlier to determine certain necessary c parameters. c c on input-- c c t contains a real value at which the derivative is to be c determined. c c n contains the number of points which were specified to c determine the curve. c c x and y are arrays containing the abscissae and c ordinates, respectively, of the specified points. c c yp is an array of second derivative values of the curve c at the nodes. c c and c c sigma contains the tension factor (its sign is ignored). c c the parameters n, x, y, yp, and sigma should be input c unaltered from the output of curv1. c c on output-- c c curvd contains the derivative value. c c none of the input parameters are altered. c c this function references package modules intrvl and c snhcsh. c c----------------------------------------------------------- c c determine interval c im1 = intrvl(t,x,n) i = im1+1 c c denormalize tension factor c sigmap = abs(sigma)*float(n-1)/(x(n)-x(1)) c c set up and perform differentiation c del1 = t-x(im1) del2 = x(i)-t dels = x(i)-x(im1) sum = (y(i)-y(im1))/dels if (sigmap .ne. 0.) go to 1 curvd = sum+(yp(i)*(2.*del1*del1-del2*(del1+dels))- * yp(im1)*(2.*del2*del2-del1*(del2+dels))) * /(6.*dels) return 1 sigdel = sigmap*dels call snhcsh (ss,dummy,sigdel,-1) call snhcsh (dummy,c1,sigmap*del1,1) call snhcsh (dummy,c2,sigmap*del2,1) curvd = sum+(yp(i)*(c1-ss)-yp(im1)*(c2-ss))/ * (sigdel*sigmap*(1.+ss)) return end function curvi (xl,xu,n,x,y,yp,sigma) c integer n real xl,xu,x(n),y(n),yp(n),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this function integrates a curve specified by a spline c under tension between two given limits. the subroutine c curv1 should be called earlier to determine necessary c parameters. c c on input-- c c xl and xu contain the upper and lower limits of inte- c gration, respectively. (sl need not be less than or c equal to xu, curvi (xl,xu,...) .eq. -curvi (xu,xl,...) ). c c n contains the number of points which were specified to c determine the curve. c c x and y are arrays containing the abscissae and c ordinates, respectively, of the specified points. c c yp is an array from subroutine curv1 containing c the values of the second derivatives at the nodes. c c and c c sigma contains the tension factor (its sign is ignored). c c the parameters n, x, y, yp, and sigma should be input c unaltered from the output of curv1. c c on output-- c c curvi contains the integral value. c c none of the input parameters are altered. c c this function references package modules intrvl and c snhcsh. c c----------------------------------------------------------- c c denormalize tension factor c sigmap = abs(sigma)*float(n-1)/(x(n)-x(1)) c c determine actual upper and lower bounds c xxl = xl xxu = xu ssign = 1. if (xl .lt. xu) go to 1 xxl = xu xxu = xl ssign = -1. if (xl .gt. xu) go to 1 c c return zero if xl .eq. xu c curvi = 0. return c c search for proper intervals c 1 ilm1 = intrvl (xxl,x,n) il = ilm1+1 ium1 = intrvl (xxu,x,n) iu = ium1+1 if (il .eq. iu) go to 8 c c integrate from xxl to x(il) c sum = 0. if (xxl .eq. x(il)) go to 3 del1 = xxl-x(ilm1) del2 = x(il)-xxl dels = x(il)-x(ilm1) t1 = (del1+dels)*del2/(2.*dels) t2 = del2*del2/(2.*dels) sum = t1*y(il)+t2*y(ilm1) if (sigma .eq. 0.) go to 2 call snhcsh (dummy,c1,sigmap*del1,2) call snhcsh (dummy,c2,sigmap*del2,2) call snhcsh (ss,cs,sigmap*dels,3) sum = sum+((dels*dels*(cs-ss/2.)-del1*del1*(c1-ss/2.)) * *yp(il)+del2*del2*(c2-ss/2.)*yp(ilm1))/ * (sigmap*sigmap*dels*(1.+ss)) go to 3 2 sum = sum-t1*t1*dels*yp(il)/6. * -t2*(del1*(del2+dels)+dels*dels)*yp(ilm1)/12. c c integrate over interior intervals c 3 if (iu-il .eq. 1) go to 6 ilp1 = il+1 do 5 i = ilp1,ium1 dels = x(i)-x(i-1) sum = sum+(y(i)+y(i-1))*dels/2. if (sigma .eq. 0.) go to 4 call snhcsh (ss,cs,sigmap*dels,3) sum = sum+(yp(i)+yp(i-1))*dels*(cs-ss/2.)/ * (sigmap*sigmap*(1.+ss)) go to 5 4 sum = sum-(yp(i)+yp(i-1))*dels*dels*dels/24. 5 continue c c integrate from x(iu-1) to xxu c 6 if (xxu .eq. x(ium1)) go to 10 del1 = xxu-x(ium1) del2 = x(iu)-xxu dels = x(iu)-x(ium1) t1 = del1*del1/(2.*dels) t2 = (del2+dels)*del1/(2.*dels) sum = sum+t1*y(iu)+t2*y(ium1) if (sigma .eq. 0.) go to 7 call snhcsh (dummy,c1,sigmap*del1,2) call snhcsh (dummy,c2,sigmap*del2,2) call snhcsh (ss,cs,sigmap*dels,3) sum = sum+(yp(iu)*del1*del1*(c1-ss/2.)+yp(ium1)* * (dels*dels*(cs-ss/2.)-del2*del2*(c2-ss/2.))) * /(sigmap*sigmap*dels*(1.+ss)) go to 10 7 sum = sum-t1*(del2*(del1+dels)+dels*dels)*yp(iu)/12. * -t2*t2*dels*yp(ium1)/6. go to 10 c c integrate from xxl to xxu c 8 delu1 = xxu-x(ium1) delu2 = x(iu)-xxu dell1 = xxl-x(ium1) dell2 = x(iu)-xxl dels = x(iu)-x(ium1) deli = xxu-xxl t1 = (delu1+dell1)*deli/(2.*dels) t2 = (delu2+dell2)*deli/(2.*dels) sum = t1*y(iu)+t2*y(ium1) if (sigma .eq. 0.) go to 9 call snhcsh (dummy,cu1,sigmap*delu1,2) call snhcsh (dummy,cu2,sigmap*delu2,2) call snhcsh (dummy,cl1,sigmap*dell1,2) call snhcsh (dummy,cl2,sigmap*dell2,2) call snhcsh (ss,dummy,sigmap*dels,-1) sum = sum+(yp(iu)*(delu1*delu1*(cu1-ss/2.) * -dell1*dell1*(cl1-ss/2.)) * +yp(ium1)*(dell2*dell2*(cl2-ss/2.) * -delu2*delu2*(cu2-ss/2.)))/ * (sigmap*sigmap*dels*(1.+ss)) go to 10 9 sum = sum-t1*(delu2*(dels+delu1)+dell2*(dels+dell1))* * yp(iu)/12. * -t2*(dell1*(dels+dell2)+delu1*(dels+delu2))* * yp(ium1)/12. c c correct sign and return c 10 curvi = ssign*sum return end subroutine curvp1 (n,x,y,p,yp,temp,sigma,ierr) c integer n,ierr real x(n),y(n),p,yp(n),temp(1),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine determines the parameters necessary to c compute a periodic interpolatory spline under tension c through a sequence of functional values. for actual ends c of the curve may be specified or omitted. for actual c computation of points on the curve it is necessary to call c the function curvp2. c c on input-- c c n is the number of values to be interpolated (n.ge.2). c c x is an array of the n increasing abscissae of the c functional values. c c y is an array of the n ordinates of the values, (i. e. c y(k) is the functional value corresponding to x(k) ). c c p is the period (p .gt. x(n)-x(1)). c c yp is an array of length at least n. c c temp is an array of length at least 2*n which is used c for scratch storage. c c and c c sigma contains the tension factor. this value indicates c the curviness desired. if abs(sigma) is nearly zero c (e.g. .001) the resulting curve is approximately a c cubic spline. if abs(sigma) is large (e.g. 50.) the c resulting curve is nearly a polygonal line. if sigma c equals zero a cubic spline results. a standard value c for sigma is approximately 1. in absolute value. c c on output-- c c yp contains the values of the second derivative of the c curve at the given nodes. c c ierr contains an error flag, c = 0 for normal return, c = 1 if n is less than 2, c = 2 if p is less than or equal to x(n)-x(1), c = 3 if x-values are not strictly increasing. c c and c c n, x, y, and sigma are unaltered. c c this subroutine references package modules terms and c snhcsh. c c----------------------------------------------------------- c nm1 = n-1 np1 = n+1 ierr = 0 if (n .le. 1) go to 6 if (p .le. x(n)-x(1) .or. p .le. 0.) go to 7 c c denormalize tension factor c sigmap = abs(sigma)*float(n)/p c c set up right hand side and tridiagonal system for yp and c perform forward elimination c delx1 = p-(x(n)-x(1)) dx1 = (y(1)-y(n))/delx1 call terms (diag1,sdiag1,sigmap,delx1) delx2 = x(2)-x(1) if (delx2 .le. 0.) go to 8 dx2 = (y(2)-y(1))/delx2 call terms (diag2,sdiag2,sigmap,delx2) diag = diag1+diag2 yp(1) = (dx2-dx1)/diag temp(np1) = -sdiag1/diag temp(1) = sdiag2/diag dx1 = dx2 diag1 = diag2 sdiag1 = sdiag2 if (n .eq. 2) go to 2 do 1 i = 2,nm1 npi = n+i delx2 = x(i+1)-x(i) if (delx2 .le. 0.) go to 8 dx2 = (y(i+1)-y(i))/delx2 call terms (diag2,sdiag2,sigmap,delx2) diag = diag1+diag2-sdiag1*temp(i-1) yp(i) = (dx2-dx1-sdiag1*yp(i-1))/diag temp(npi) = -temp(npi-1)*sdiag1/diag temp(i) = sdiag2/diag dx1 = dx2 diag1 = diag2 1 sdiag1 = sdiag2 2 delx2 = p-(x(n)-x(1)) dx2 = (y(1)-y(n))/delx2 call terms (diag2,sdiag2,sigmap,delx2) yp(n) = dx2-dx1 temp(nm1) = temp(2*n-1)-temp(nm1) if (n .eq. 2) go to 4 c c perform first step of back substitution c do 3 i = 3,n ibak = np1-i npibak =n+ibak yp(ibak) = yp(ibak)-temp(ibak)*yp(ibak+1) 3 temp(ibak) =temp(npibak)-temp(ibak)*temp(ibak+1) 4 yp(n) = (yp(n)-sdiag2*yp(1)-sdiag1*yp(nm1))/ * (diag1+diag2+sdiag2*temp(1)+sdiag1*temp(nm1)) c c perform second step of back substitution c ypn = yp(n) do 5 i = 1,nm1 5 yp(i) = yp(i)+temp(i)*ypn return c c too few points c 6 ierr = 1 return c c period too small c 7 ierr = 2 return c c x-values not strictly increasing c 8 ierr = 3 return end subroutine curvps (n,x,y,p,d,isw,s,eps,ys,ysp,sigma, * temp,ierr) c integer n,isw,ierr real x(n),y(n),p,d(n),s,eps,ys(n),ysp(n),sigma, * temp(n,11) c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine determines the parameters necessary to c compute a periodic smoothing spline under tension. for a c given increasing sequence of abscissae (x(i)), i = 1,...,n c and associated ordinates (y(i)), i = 1,...,n, letting p be c the period, x(n+1) = x(1)+p, and y(n+1) = y(1), the c function determined minimizes the summation from i = 1 to c n of the square of the second derivative of f plus sigma c squared times the difference of the first derivative of f c and (f(x(i+1))-f(x(i)))/(x(i+1)-x(i)) squared, over all c functions f with period p and two continuous derivatives c such that the summation of the square of c (f(x(i))-y(i))/d(i) is less than or equal to a given c constant s, where (d(i)), i = 1,...,n are a given set of c observation weights. the function determined is a periodic c spline under tension with third derivative discontinuities c at (x(i)) i = 1,...,n (and all periodic translations of c these values). for actual computation of points on the c curve it is necessary to call the function curvp2. the c determination of the curve is performed by subroutine c curvpp, the subroutin curvps only decomposes the workspace c for curvpp. c c on input-- c c n is the number of values to be smoothed (n.ge.2). c c x is an array of the n increasing abscissae of the c values to be smoothed. c c y is an array of the n ordinates of the values to be c smoothed, (i. e. y(k) is the functional value c corresponding to x(k) ). c c p is the period (p .gt. x(n)-x(1)). c c d is a parameter containing the observation weights. c this may either be an array of length n or a scalar c (interpreted as a constant). the value of d c corresponding to the observation (x(k),y(k)) should c be an approximation to the standard deviation of error. c c isw contains a switch indicating whether the parameter c d is to be considered a vector or a scalar, c = 0 if d is an array of length n, c = 1 if d is a scalar. c c s contains the value controlling the smoothing. this c must be non-negative. for s equal to zero, the c subroutine does interpolation, larger values lead to c smoother funtions. if parameter d contains standard c deviation estimates, a reasonable value for s is c float(n). c c eps contains a tolerance on the relative precision to c which s is to be interpreted. this must be greater than c or equal to zero and less than or equal to one. a c reasonable value for eps is sqrt(2./float(n)). c c ys is an array of length at least n. c c ysp is an array of length at least n. c c sigma contains the tension factor. this value indicates c the degree to which the first derivative part of the c smoothing functional is emphasized. if sigma is nearly c zero (e. g. .001) the resulting curve is approximately a c cubic spline. if sigma is large (e. g. 50.) the c resulting curve is nearly a polygonal line. if sigma c equals zero a cubic spline results. a standard value for c sigma is approximately 1. c c and c c temp is an array of length at least 11*n which is used c for scratch storage. c c on output-- c c ys contains the smoothed ordinate values. c c ysp contains the values of the second derivative of the c smoothed curve at the given nodes. c c ierr contains an error flag, c = 0 for normal return, c = 1 if n is less than 2, c = 2 if s is negative, c = 3 if eps is negative or greater than one, c = 4 if x-values are not strictly increasing, c = 5 if a d-value is non-positive, c = 6 if p is less than or equal to x(n)-x(1). c c and c c n, x, y, p, d, isw, s, eps, and sigma are unaltered. c c this subroutine references package modules curvpp, terms, c and snhcsh. c c----------------------------------------------------------- c c decompose temp into eleven arrays and call curvpp c call curvpp (n,x,y,p,d,isw,s,eps,ys,ysp,sigma, * temp(1,1),temp(1,2),temp(1,3),temp(1,4), * temp(1,5),temp(1,6),temp(1,7),temp(1,8), * temp(1,9),temp(1,10),temp(1,11),ierr) return end function curvp2 (t,n,x,y,p,yp,sigma) c integer n real t,x(n),y(n),p,yp(n),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this function interpolates a curve at a given point using c a periodic spline under tension. the subroutine curvp1 c should be called earlier to determine certain necessary c parameters. c c on input-- c c t contains a real value to be mapped onto the interpo- c lating curve. c c n contains the number of points which were specified to c determine the curve. c c x and y are arrays containing the abscissae and c ordinates, respectively, of the specified points. c c p contains the period. c c yp is an array of second derivative values of the curve c at the nodes. c c and c c sigma contains the tension factor (its sign is ignored). c c the parameters n, x, y, p, yp, and sigma should be input c unaltered from the output of curvp1. c c on output-- c c curvp2 contains the interpolated value. c c none of the input parameters are altered. c c this function references package modules intrvp and c snhcsh. c c----------------------------------------------------------- c c determine interval c im1 = intrvp (t,x,n,p,tp) i = im1+1 c c denormalize tension factor c sigmap = abs(sigma)*float(n)/p c c set up and perform interpolation c del1 = tp-x(im1) if (im1 .eq. n) go to 1 del2 = x(i)-tp dels = x(i)-x(im1) go to 2 1 i = 1 del2 = x(1)+p-tp dels = p-(x(n)-x(1)) 2 sum = (y(i)*del1+y(im1)*del2)/dels if (sigmap .ne. 0.) go to 3 curvp2 = sum-del1*del2*(yp(i)*(del1+dels)+yp(im1)* * (del2+dels))/(6.*dels) return 3 sigdel = sigmap*dels call snhcsh (ss,dummy,sigdel,-1) call snhcsh (s1,dummy,sigmap*del1,-1) call snhcsh (s2,dummy,sigmap*del2,-1) curvp2 = sum+(yp(i)*del1*(s1-ss)+yp(im1)*del2*(s2-ss))/ * (sigdel*sigmap*(1.+ss)) return end function curvpi (xl,xu,n,x,y,p,yp,sigma) c integer n real xl,xu,x(n),y(n),p,yp(n),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this function integrates a curve specified by a periodic c spline under tension between two given limits. the c subroutine curvp1 should be called earlier to determine c necessary parameters. c c on input-- c c xl and xu contain the upper and lower limits of inte- c gration, respectively. (sl need not be less than or c equal to xu, curvpi (xl,xu,...) .eq. -curvpi (xu,xl,...) ). c c n contains the number of points which were specified to c determine the curve. c c x and y are arrays containing the abscissae and c ordinates, respectively, of the specified points. c c p contains the period. c c yp is an array from subroutine curvp1 containing c the values of the second derivatives at the nodes. c c and c c sigma contains the tension factor (its sign is ignored). c c the parameters n, x, y, p, yp, and sigma should be input c unaltered from the output of curvp1. c c on output-- c c c curvpi contains the integral value. c c none of the input parameters are altered. c c this function references package modules intrvp and c snhcsh. c c-------------------------------------------------------------- c integer uper logical bdy c c denormalize tension factor c sigmap = abs(sigma)*float(n)/p c c determine actual upper and lower bounds c x1pp = x(1)+p isign = 1 ilm1 = intrvp (xl,x,n,p,xxl) lper = int((xl-x(1))/p) if (xl .lt. x(1)) lper = lper-1 ium1 = intrvp (xu,x,n,p,xxu) uper = int((xu-x(1))/p) if (xu .lt. x(1)) uper = uper-1 ideltp = uper-lper bdy = float(ideltp)*(xxu-xxl) .lt. 0. if ((ideltp .eq. 0 .and. xxu .lt. xxl) .or. * ideltp .lt. 0) isign = -1 if (bdy) ideltp = ideltp-isign if (xxu .ge. xxl) go to 1 xsave = xxl xxl = xxu xxu = xsave isave = ilm1 ilm1 = ium1 ium1 = isave 1 il = ilm1+1 if (ilm1 .eq. n) il = 1 xil = x(il) if (ilm1 .eq. n) xil = x1pp iu = ium1+1 if (ium1 .eq. n) iu = 1 xiu = x(iu) if (ium1 .eq. n) xiu = x1pp s1 = 0. if (ilm1 .eq. 1 .or. (ideltp .eq. 0 .and. * .not. bdy)) go to 4 c c integrate from x(1) to x(ilm1), store in s1 c do 3 i = 2,ilm1 dels = x(i)-x(i-1) s1 = s1+(y(i)+y(i-1))*dels/2. if (sigma .eq. 0.) go to 2 call snhcsh (ss,cs,sigmap*dels,3) s1 = s1+(yp(i)+yp(i-1))*dels*(cs-ss/2.)/ * (sigmap*sigmap*(1.+ss)) go to 3 2 s1 = s1-(yp(i)+yp(i-1))*dels*dels*dels/24. 3 continue 4 s2 = 0. if (x(ilm1) .ge. xxl .or. (ideltp .eq. 0 * .and. .not. bdy)) go to 6 c c integrate from x(ilm1) to xxl, store in s2 c del1 = xxl-x(ilm1) del2 = xil-xxl dels = xil-x(ilm1) t1 = del1*del1/(2.*dels) t2 = (del2+dels)*del1/(2.*dels) s2 = t1*y(il)+t2*y(ilm1) if (sigma .eq. 0.) go to 5 call snhcsh (dummy,c1,sigmap*del1,2) call snhcsh (dummy,c2,sigmap*del2,2) call snhcsh (ss,cs,sigmap*dels,3) s2 = s2+(yp(il)*del1*del1*(c1-ss/2.)+yp(ilm1)* * (dels*dels*(cs-ss/2.)-del2*del2*(c2-ss/2.))) * /(sigmap*sigmap*dels*(1.+ss)) go to 6 5 s2 = s2-t1*(del2*(del1+dels) * +dels*dels)*yp(il)/12. * -t2*t2*dels*yp(ilm1)/6. 6 s3 = 0. if (xxl .ge. xil .or. (ideltp .eq. 0 .and. bdy) * .or. ilm1 .eq. ium1) go to 8 c c integrate from xxl to xil, store in s3 c del1 = xxl-x(ilm1) del2 = xil-xxl dels = xil-x(ilm1) t1 = (del1+dels)*del2/(2.*dels) t2 = del2*del2/(2.*dels) s3 = t1*y(il)+t2*y(ilm1) if (sigma .eq. 0.) go to 7 call snhcsh (dummy,c1,sigmap*del1,2) call snhcsh (dummy,c2,sigmap*del2,2) call snhcsh (ss,cs,sigmap*dels,3) s3 = s3+((dels*dels*(cs-ss/2.)-del1*del1*(c1-ss/2.)) * *yp(il)+del2*del2*(c2-ss/2.)*yp(ilm1))/ * (sigmap*sigmap*dels*(1.+ss)) go to 8 7 s3 = s3-t1*t1*dels*yp(il)/6. * -t2*(del1*(del2+dels)+dels*dels)* * yp(ilm1)/12. 8 s4 = 0. if (ilm1 .ge. ium1-1 .or. (ideltp .eq. 0 .and. bdy)) * go to 11 c c integrate from xil to x(ium1), store in s4 c ilp1 = il+1 do 10 i = ilp1,ium1 dels = x(i)-x(i-1) s4 = s4+(y(i)+y(i-1))*dels/2. if (sigma .eq. 0.) go to 9 call snhcsh (ss,cs,sigmap*dels,3) s4 = s4+(yp(i)+yp(i-1))*dels*(cs-ss/2.)/ * (sigmap*sigmap*(1.+ss)) go to 10 9 s4 = s4-(yp(i)+yp(i-1))*dels*dels*dels/24. 10 continue 11 s5 = 0. if (x(ium1) .ge. xxu .or. (ideltp .eq. 0 .and. bdy) * .or. ilm1 .eq. ium1) go to 13 c c integrate from x(ium1) to xxu, store in s5 c del1 = xxu-x(ium1) del2 = xiu-xxu dels = xiu-x(ium1) t1 = del1*del1/(2.*dels) t2 = (del2+dels)*del1/(2.*dels) s5 = t1*y(iu)+t2*y(ium1) if (sigma .eq. 0.) go to 12 call snhcsh (dummy,c1,sigmap*del1,2) call snhcsh (dummy,c2,sigmap*del2,2) call snhcsh (ss,cs,sigmap*dels,3) s5 = s5+(yp(iu)*del1*del1*(c1-ss/2.)+yp(ium1)* * (dels*dels*(cs-ss/2.)-del2*del2*(c2-ss/2.))) * /(sigmap*sigmap*dels*(1.+ss)) go to 13 12 s5 = s5-t1*(del2*(del1+dels) * +dels*dels)*yp(iu)/12. * -t2*t2*dels*yp(ium1)/6. 13 s6 = 0. if (xxu .ge. xiu .or. (ideltp .eq. 0 .and. * .not. bdy)) go to 15 c c integrate from xxu to xiu, store in s6 c del1 = xxu-x(ium1) del2 = xiu-xxu dels = xiu-x(ium1) t1 = (del1+dels)*del2/(2.*dels) t2 = del2*del2/(2.*dels) s6 = t1*y(iu)+t2*y(ium1) if (sigma .eq. 0.) go to 14 call snhcsh (dummy,c1,sigmap*del1,2) call snhcsh (dummy,c2,sigmap*del2,2) call snhcsh (ss,cs,sigmap*dels,3) s6 = s6+((dels*dels*(cs-ss/2.)-del1*del1*(c1-ss/2.)) * *yp(iu)+del2*del2*(c2-ss/2.)*yp(ium1))/ * (sigmap*sigmap*dels*(1.+ss)) go to 15 14 s6 = s6-t1*t1*dels*yp(iu)/6. * -t2*(del1*(del2+dels)+dels*dels)* * yp(ium1)/12. 15 s7 = 0. if (iu .eq. 1 .or. (ideltp .eq. 0 .and. .not. bdy)) * go to 18 c c integrate from xiu to x1pp, store in s7 c np1 = n+1 iup1 = iu+1 do 17 ii = iup1,np1 im1 = ii-1 i = ii if (i .eq. np1) i=1 dels = x(i)-x(im1) if (dels .le. 0.) dels=dels+p s7 = s7+(y(i)+y(im1))*dels/2. if (sigma .eq. 0.) go to 16 call snhcsh (ss,cs,sigmap*dels,3) s7 = s7+(yp(i)+yp(im1))*dels*(cs-ss/2.)/ * (sigmap*sigmap*(1.+ss)) go to 17 16 s7 = s7-(yp(i)+yp(im1))*dels*dels*dels/24. 17 continue 18 s8 = 0. if (ilm1 .lt. ium1 .or. (ideltp .eq. 0 .and. bdy)) * go to 20 c c integrate from xxl to xxu, store in s8 c delu1 = xxu-x(ium1) delu2 = xiu-xxu dell1 = xxl-x(ium1) dell2 = xiu-xxl dels = xiu-x(ium1) deli = xxu-xxl t1 = (delu1+dell1)*deli/(2.*dels) t2 = (delu2+dell2)*deli/(2.*dels) s8 = t1*y(iu)+t2*y(ium1) if (sigma .eq. 0.) go to 19 call snhcsh (dummy,cu1,sigmap*delu1,2) call snhcsh (dummy,cu2,sigmap*delu2,2) call snhcsh (dummy,cl1,sigmap*dell1,2) call snhcsh (dummy,cl2,sigmap*dell2,2) call snhcsh (ss,dummy,sigmap*dels,-1) s8 = s8+(yp(iu)*(delu1*delu1*(cu1-ss/2.) * -dell1*dell1*(cl1-ss/2.)) * +yp(ium1)*(dell2*dell2*(cl2-ss/2.) * -delu2*delu2*(cu2-ss/2.)))/ * (sigmap*sigmap*dels*(1.+ss)) go to 20 19 s8 = s8-t1*(delu2*(dels+delu1) * +dell2*(dels+dell1))*yp(iu)/12. * -t2*(dell1*(dels+dell2) * +delu1*(dels+delu2))*yp(ium1)/12. 20 so = s1+s2+s6+s7 si = s3+s4+s5+s8 if (bdy) go to 21 curvpi = float(ideltp)*(so+si)+float(isign)*si return 21 curvpi = float(ideltp)*(so+si)+float(isign)*so return end subroutine kurv1 (n,x,y,slp1,slpn,islpsw,xp,yp,temp,s, * sigma,ierr) c integer n,islpsw,ierr real x(n),y(n),slp1,slpn,xp(n),yp(n),temp(n),s(n), * sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine determines the parameters necessary to c compute a spline under tension forming a curve in the c plane and passing through a sequence of pairs (x(1),y(1)), c ...,(x(n),y(n)). for actual computation of points on the c curve it is necessary to call the subroutine kurv2. c c on input-- c c n is the number of points to be interpolated (n.ge.2). c c x is an array containing the n x-coordinates of the c points. c c y is an array containing the n y-coordinates of the c points. (adjacent x-y pairs must be distinct, i. e. c either x(i) .ne. x(i+1) or y(i) .ne. y(i+1), for c i = 1,...,n-1.) c c slp1 and slpn contain the desired values for the angles c (in radians) of the slope at (x(1),y(1)) and (x(n),y(n)) c respectively. the angles are measured counter-clock- c wise from the x-axis and the positive sense of the curve c is assumed to be that moving from point 1 to point n. c the user may omit values for either or both of these c parameters and signal this with islpsw. c c islpsw contains a switch indicating which slope data c should be used and which should be estimated by this c subroutine, c = 0 if slp1 and slpn are to be used, c = 1 if slp1 is to be used but not slpn, c = 2 if slpn is to be used but not slp1, c = 3 if both slp1 and slpn are to be estimated c internally. c c xp and yp are arrays of length at least n. c c temp is an array of length at least n which is used c for scratch storage. c c s is an array of length at least n. c c and c c sigma contains the tension factor. this value indicates c the curviness desired. if abs(sigma) is nearly zero c (e.g. .001) the resulting curve is approximately a cubic c spline. if abs(sigma) is large (e. g. 50.) the resulting c curve is nearly a polygonal line. if sigma equals zero a c cubic spline results. a standard value for sigma is c approximately 1. in absolute value. c c on output-- c c xp and yp contain information about the curvature of the c curve at the given nodes. c c s contains the polygonal arclengths of the curve. c c ierr contains an error flag, c = 0 for normal return, c = 1 if n is less than 2, c = 2 if adjacent coordinate pairs coincide. c c and c c n, x, y, slp1, slpn, islpsw, and sigma are unaltered. c c this subroutine references package modules ceez, terms, c and snhcsh. c c----------------------------------------------------------- c nm1 = n-1 np1 = n+1 ierr = 0 if (n .le. 1) go to 11 c c determine polygonal arclengths c s(1) = 0. do 1 i = 2,n im1 = i-1 1 s(i) = s(im1)+sqrt((x(i)-x(im1))**2+ * (y(i)-y(im1))**2) c c denormalize tension factor c sigmap = abs(sigma)*float(n-1)/s(n) c c approximate end slopes c if (islpsw .ge. 2) go to 2 slpp1x = cos(slp1) slpp1y = sin(slp1) go to 4 2 dels1 = s(2)-s(1) dels2 = dels1+dels1 if (n .gt. 2) dels2 = s(3)-s(1) if (dels1 .eq. 0. .or. dels2 .eq. 0.) go to 12 call ceez (dels1,dels2,sigmap,c1,c2,c3,n) sx = c1*x(1)+c2*x(2) sy = c1*y(1)+c2*y(2) if (n .eq. 2) go to 3 sx = sx+c3*x(3) sy = sy+c3*y(3) 3 delt = sqrt(sx*sx+sy*sy) slpp1x = sx/delt slpp1y = sy/delt 4 if (islpsw .eq. 1 .or. islpsw .eq. 3) go to 5 slppnx = cos(slpn) slppny = sin(slpn) go to 7 5 delsn = s(n)-s(nm1) delsnm = delsn+delsn if (n .gt. 2) delsnm = s(n)-s(n-2) if (delsn .eq. 0. .or. delsnm .eq. 0.) go to 12 call ceez (-delsn,-delsnm,sigmap,c1,c2,c3,n) sx = c1*x(n)+c2*x(nm1) sy = c1*y(n)+c2*y(nm1) if (n .eq. 2) go to 6 sx = sx+c3*x(n-2) sy = sy+c3*y(n-2) 6 delt = sqrt(sx*sx+sy*sy) slppnx = sx/delt slppny = sy/delt c c set up right hand sides and tridiagonal system for xp and c yp and perform forward elimination c 7 dx1 = (x(2)-x(1))/s(2) dy1 = (y(2)-y(1))/s(2) call terms (diag1,sdiag1,sigmap,s(2)) xp(1) = (dx1-slpp1x)/diag1 yp(1) = (dy1-slpp1y)/diag1 temp(1) = sdiag1/diag1 if (n .eq. 2) go to 9 do 8 i = 2,nm1 dels2 = s(i+1)-s(i) if (dels2 .eq. 0.) go to 12 dx2 = (x(i+1)-x(i))/dels2 dy2 = (y(i+1)-y(i))/dels2 call terms (diag2,sdiag2,sigmap,dels2) diag = diag1+diag2-sdiag1*temp(i-1) diagin = 1./diag xp(i) = (dx2-dx1-sdiag1*xp(i-1))*diagin yp(i) = (dy2-dy1-sdiag1*yp(i-1))*diagin temp(i) = sdiag2*diagin dx1 = dx2 dy1 = dy2 diag1 = diag2 8 sdiag1 = sdiag2 9 diag = diag1-sdiag1*temp(nm1) xp(n) = (slppnx-dx1-sdiag1*xp(nm1))/diag yp(n) = (slppny-dy1-sdiag1*yp(nm1))/diag c c perform back substitution c do 10 i = 2,n ibak = np1-i xp(ibak) = xp(ibak)-temp(ibak)*xp(ibak+1) 10 yp(ibak) = yp(ibak)-temp(ibak)*yp(ibak+1) return c c too few points c 11 ierr = 1 return c c coincident adjacent points c 12 ierr = 2 return end subroutine kurv2 (t,xs,ys,n,x,y,xp,yp,s,sigma) c integer n real t,xs,ys,x(n),y(n),xp(n),yp(n),s(n),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine performs the mapping of points in the c interval (0.,1.) onto a curve in the plane. the subroutine c kurv1 should be called earlier to determine certain c necessary parameters. the resulting curve has a parametric c representation both of whose components are splines under c tension and functions of the polygonal arclength c parameter. c c on input-- c c t contains a real value to be mapped to a point on the c curve. the interval (0.,1.) is mapped onto the entire c curve, with 0. mapping to (x(1),y(1)) and 1. mapping c to (x(n),y(n)). values outside this interval result in c extrapolation. c c n contains the number of points which were specified c to determine the curve. c c x and y are arrays containing the x- and y-coordinates c of the specified points. c c xp and yp are the arrays output from kurv1 containing c curvature information. c c s is an array containing the polygonal arclengths of c the curve. c c and c c sigma contains the tension factor (its sign is ignored). c c the parameters n, x, y, xp, yp, s, and sigma should be c input unaltered from the output of kurv1. c c on output-- c c xs and ys contain the x- and y-coordinates of the image c point on the curve. c c none of the input parameters are altered. c c this subroutine references package modules intrvl and c snhcsh. c c----------------------------------------------------------- c c determine interval c tn = s(n)*t im1 = intrvl(tn,s,n) i = im1+1 c c denormalize tension factor c sigmap = abs(sigma)*float(n-1)/s(n) c c set up and perform interpolation c del1 = tn-s(im1) del2 = s(i)-tn dels = s(i)-s(im1) sumx = (x(i)*del1+x(im1)*del2)/dels sumy = (y(i)*del1+y(im1)*del2)/dels if (sigmap .ne. 0.) go to 1 d = del1*del2/(6.*dels) c1 = (del1+dels)*d c2 = (del2+dels)*d xs = sumx-xp(i)*c1-xp(im1)*c2 ys = sumy-yp(i)*c1-yp(im1)*c2 return 1 sigdel = sigmap*dels call snhcsh(ss,dummy,sigdel,-1) call snhcsh(s1,dummy,sigmap*del1,-1) call snhcsh(s2,dummy,sigmap*del2,-1) d = sigdel*sigmap*(1.+ss) c1 = del1*(s1-ss)/d c2 = del2*(s2-ss)/d xs = sumx+xp(i)*c1+xp(im1)*c2 ys = sumy+yp(i)*c1+yp(im1)*c2 return end subroutine kurvd (t,xs,ys,xst,yst,xstt,ystt,n,x,y,xp, * yp,s,sigma) c integer n real t,xs,ys,xst,yst,xstt,ystt,x(n),y(n),xp(n),yp(n), * s(n),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine performs the mapping of points in the c interval (0.,1.) onto a curve in the plane. it also c returns the first and second derivatives of the component c functions. the subroutine kurv1 should be called earlier c to determine certain necessary parameters. the resulting c curve has a parametric representation both of whose c components are splines under tension and functions of the c polygonal arclength parameter. c c on input-- c c t contains a real value to be mapped to a point on the c curve. the interval (0.,1.) is mapped onto the entire c curve, with 0. mapping to (x(1),y(1)) and 1. mapping c to (x(n),y(n)). values outside this interval result in c extrapolation. c c n contains the number of points which were specified c to determine the curve. c c x and y are arrays containing the x- and y-coordinates c of the specified points. c c xp and yp are the arrays output from kurv1 containing c curvature information. c c s is an array containing the polygonal arclengths of c the curve. c c and c c sigma contains the tension factor (its sign is ignored). c c the parameters n, x, y, xp, yp, s, and sigma should be c input unaltered from the output of kurv1. c c on output-- c c xs and ys contain the x- and y-coordinates of the image c point on the curve. xst and yst contain the first c derivatives of the x- and y-components of the mapping c with respect to t. xstt and ystt contain the second c derivatives of the x- and y-components of the mapping c with respect to t. c c none of the input parameters are altered. c c this subroutine references package modules intrvl and c snhcsh. c c----------------------------------------------------------- c c determine interval c tn = s(n)*t im1 = intrvl(tn,s,n) i = im1+1 c c denormalize tension factor c sigmap = abs(sigma)*float(n-1)/s(n) c c set up and perform interpolation c del1 = tn-s(im1) del2 = s(i)-tn dels = s(i)-s(im1) sumx = (x(i)*del1+x(im1)*del2)/dels sumy = (y(i)*del1+y(im1)*del2)/dels sumxt = s(n)*(x(i)-x(im1))/dels sumyt = s(n)*(y(i)-y(im1))/dels if (sigmap .ne. 0.) go to 1 dels6 = 6.*dels d = del1*del2/dels6 c1 = -(del1+dels)*d c2 = -(del2+dels)*d dels6 = dels6/s(n) ct1 = (2.*del1*del1-del2*(del1+dels))/dels6 ct2 = -(2.*del2*del2-del1*(del2+dels))/dels6 dels = dels/(s(n)*s(n)) ctt1 = del1/dels ctt2 = del2/dels go to 2 1 sigdel = sigmap*dels call snhcsh (ss,dummy,sigdel,-1) call snhcsh (s1,co1,sigmap*del1,0) call snhcsh (s2,co2,sigmap*del2,0) d = sigdel*sigmap*(1.+ss) c1 = del1*(s1-ss)/d c2 = del2*(s2-ss)/d ct1 = (co1-ss)*s(n)/d ct2 = -(co2-ss)*s(n)/d ctt1 = del1*(1.+s1)*s(n)*s(n)/(dels*(1.+ss)) ctt2 = del2*(1.+s2)*s(n)*s(n)/(dels*(1.+ss)) 2 xs = sumx+c1*xp(i)+c2*xp(im1) ys = sumy+c1*yp(i)+c2*yp(im1) xst = sumxt+ct1*xp(i)+ct2*xp(im1) yst = sumyt+ct1*yp(i)+ct2*yp(im1) xstt = ctt1*xp(i)+ctt2*xp(im1) ystt = ctt1*yp(i)+ctt2*yp(im1) return end subroutine kurvp1 (n,x,y,xp,yp,temp,s,sigma,ierr) c integer n,ierr real x(n),y(n),xp(n),yp(n),temp(1),s(n),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine determines the parameters necessary to c compute a spline under tension forming a closed curve in c the plane and passing through a sequence of pairs c (x(1),y(1)),...,(x(n),y(n)). for actual computation of c points on the curve it is necessary to call the subroutine c kurvp2. c c on input-- c c n is the number of points to be interpolated (n.ge.2). c c x is an array containing the n x-coordinates of the c points. c c y is an array containing the n y-coordinates of the c points. (adjacent x-y pairs must be distinct, i. e. c either x(i) .ne. x(i+1) or y(i) .ne. y(i+1), for c i = 1,...,n-1 and either x(1) .ne. x(n) or y(1) .ne. y(n).) c c xp and yp are arrays of length at least n. c c temp is an array of length at least 2*n which is used c for scratch storage. c c s is an array of length at least n. c c and c c sigma contains the tension factor. this value indicates c the curviness desired. if abs(sigma) is nearly zero c (e.g. .001) the resulting curve is approximately a cubic c spline. if abs(sigma) is large (e. g. 50.) the resulting c curve is nearly a polygonal line. if sigma equals zero a c cubic spline results. a standard value for sigma is c approximately 1. in absolute value. c c on output-- c c xp and yp contain information about the curvature of the c curve at the given nodes. c c s contains the polygonal arclengths of the curve. c c ierr contains an error flag, c = 0 for normal return, c = 1 if n is less than 2, c = 2 if adjacent coordinate pairs coincide. c c and c c n, x, y, and sigma are unaltered, c c this subroutine references package modules terms and c snhcsh. c c----------------------------------------------------------- c nm1 = n-1 np1 = n+1 ierr = 0 if (n .le. 1) go to 7 c c determine polygonal arclengths c s(1) = sqrt((x(n)-x(1))**2+(y(n)-y(1))**2) do 1 i = 2,n im1 = i-1 1 s(i) = s(im1)+sqrt((x(i)-x(im1))**2+ * (y(i)-y(im1))**2) c c denormalize tension factor c sigmap = abs(sigma)*float(n)/s(n) c c set up right hand sides of tridiagonal (with corner c elements) linear system for xp and yp c dels1 = s(1) if (dels1 .eq. 0.) go to 8 dx1 = (x(1)-x(n))/dels1 dy1 = (y(1)-y(n))/dels1 call terms(diag1,sdiag1,sigmap,dels1) dels2 = s(2)-s(1) if (dels2 .eq. 0.) go to 8 dx2 = (x(2)-x(1))/dels2 dy2 = (y(2)-y(1))/dels2 call terms(diag2,sdiag2,sigmap,dels2) diag = diag1+diag2 diagin = 1./diag xp(1) = (dx2-dx1)*diagin yp(1) = (dy2-dy1)*diagin temp(np1) = -sdiag1*diagin temp(1) = sdiag2*diagin dx1 = dx2 dy1 = dy2 diag1 = diag2 sdiag1 = sdiag2 if (n .eq. 2) go to 3 do 2 i = 2,nm1 npi = n+i dels2 = s(i+1)-s(i) if (dels2 .eq. 0.) go to 8 dx2 = (x(i+1)-x(i))/dels2 dy2 = (y(i+1)-y(i))/dels2 call terms(diag2,sdiag2,sigmap,dels2) diag = diag1+diag2-sdiag1*temp(i-1) diagin = 1./diag xp(i) = (dx2-dx1-sdiag1*xp(i-1))*diagin yp(i) = (dy2-dy1-sdiag1*yp(i-1))*diagin temp(npi) = -temp(npi-1)*sdiag1*diagin temp(i) = sdiag2*diagin dx1 = dx2 dy1 = dy2 diag1 = diag2 2 sdiag1 = sdiag2 3 dels2 = s(1) dx2 = (x(1)-x(n))/dels2 dy2 = (y(1)-y(n))/dels2 call terms(diag2,sdiag2,sigmap,dels2) xp(n) = dx2-dx1 yp(n) = dy2-dy1 temp(nm1) = temp(2*n-1)-temp(nm1) if (n.eq.2) go to 5 c c perform first step of back substitution c do 4 i = 3,n ibak = np1-i npibak = n+ibak xp(ibak) = xp(ibak)-temp(ibak)*xp(ibak+1) yp(ibak) = yp(ibak)-temp(ibak)*yp(ibak+1) 4 temp(ibak) = temp(npibak)-temp(ibak)*temp(ibak+1) 5 xp(n) = (xp(n)-sdiag2*xp(1)-sdiag1*xp(nm1))/ * (diag1+diag2+sdiag2*temp(1)+sdiag1*temp(nm1)) yp(n) = (yp(n)-sdiag2*yp(1)-sdiag1*yp(nm1))/ * (diag1+diag2+sdiag2*temp(1)+sdiag1*temp(nm1)) c c perform second step of back substitution c xpn = xp(n) ypn = yp(n) do 6 i = 1,nm1 xp(i) = xp(i)+temp(i)*xpn 6 yp(i) = yp(i)+temp(i)*ypn return c c too few points c 7 ierr = 1 return c c coincident adjacent points c 8 ierr = 2 return end subroutine kurvp2 (t,xs,ys,n,x,y,xp,yp,s,sigma) c integer n real t,xs,ys,x(n),y(n),xp(n),yp(n),s(n),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine performs the mapping of points in the c interval (0.,1.) onto a closed curve in the plane. the c subroutine kurvp1 should be called earlier to determine c certain necessary parameters. the resulting curve has a c parametric representation both of whose components are c periodic splines under tension and functions of the poly- c gonal arclength parameter. c c on input-- c c t contains a value to be mapped onto the curve. the c interval (0.,1.) is mapped onto the entire closed curve c with both 0. and 1. mapping to (x(1),y(1)). the mapping c is periodic with period one thus any interval of the c form (tt,tt+1.) maps onto the entire curve. c c n contains the number of points which were specified c to determine the curve. c c x and y are arrays containing the x- and y-coordinates c of the specified points. c c xp and yp are the arrays output from kurvp1 containing c curvature information. c c s is an array containing the polygonal arclengths of c the curve. c c and c c sigma contains the tension factor (its sign is ignored). c c the parameters n, x, y, xp, yp, s and sigma should c be input unaltered from the output of kurvp1. c c on output-- c c xs and ys contain the x- and y-coordinates of the image c point on the curve. c c none of the input parameters are altered. c c this subroutine references package modules intrvl and c snhcsh. c c----------------------------------------------------------- c c determine interval c tn = t-float(ifix(t)) if (tn .lt. 0.) tn = tn+1. tn = s(n)*tn+s(1) im1 = n if (tn .lt. s(n)) im1 = intrvl(tn,s,n) i = im1+1 if (i .gt. n) i = 1 c c denormalize tension factor c sigmap = abs(sigma)*float(n)/s(n) c c set up and perform interpolation c si = s(i) if (im1 .eq. n) si = s(n)+s(1) del1 = tn-s(im1) del2 = si-tn dels = si-s(im1) sumx = (x(i)*del1+x(im1)*del2)/dels sumy = (y(i)*del1+y(im1)*del2)/dels if (sigmap .ne. 0.) go to 1 d = del1*del2/(6.*dels) c1 = (del1+dels)*d c2 = (del2+dels)*d xs = sumx-xp(i)*c1-xp(im1)*c2 ys = sumy-yp(i)*c1-yp(im1)*c2 return 1 sigdel = sigmap*dels call snhcsh(ss,dummy,sigdel,-1) call snhcsh(s1,dummy,sigmap*del1,-1) call snhcsh(s2,dummy,sigmap*del2,-1) d = sigdel*sigmap*(1.+ss) ci = del1*(s1-ss)/d cim1 = del2*(s2-ss)/d xs = sumx+xp(i)*ci+xp(im1)*cim1 ys = sumy+yp(i)*ci+yp(im1)*cim1 return end subroutine kurvpd (t,xs,ys,xst,yst,xstt,ystt,n,x,y,xp, * yp,s,sigma) c integer n real t,xs,ys,xst,yst,xstt,ystt,x(n),y(n),xp(n),yp(n), * s(n),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine performs the mapping of points in the c interval (0.,1.) onto a closed curve in the plane. it also c returns the first and second derivatives of the component c functions. the subroutine kurvp1 should be called earlier c to determine certain necessary parameters. the resulting c curve has a parametric representation both of whose c components are periodic splines under tension and c functions of the polygonal arclength parameter. c c on input-- c c t contains a value to be mapped onto the curve. the c interval (0.,1.) is mapped onto the entire closed curve c with both 0. and 1. mapping to (x(1),y(1)). the mapping c is periodic with period one thus any interval of the c form (tt,tt+1.) maps onto the entire curve. c c n contains the number of points which were specified c to determine the curve. c c x and y are arrays containing the x- and y-coordinates c of the specified points. c c xp and yp are the arrays output from kurvp1 containing c curvature information. c c s is an array containing the polygonal arclengths of c the curve. c c and c c sigma contains the tension factor (its sign is ignored). c c the parameters n, x, y, xp, yp, s and sigma should c be input unaltered from the output of kurvp1. c c on output-- c c xs and ys contain the x- and y-coordinates of the image c point on the curve. xst and yst contain the first c derivatives of the x- and y-components of the mapping c with respect to t. xstt and ystt contain the second c derivatives of the x- and y-components of the mapping c with respect to t. c c none of the input parameters are altered. c c this subroutine references package modules intrvl and c snhcsh. c c----------------------------------------------------------- c c determine interval c tn = t-float(ifix(t)) if (tn .lt. 0.) tn = tn+1. tn = s(n)*tn+s(1) im1 = n if (tn .lt. s(n)) im1 = intrvl(tn,s,n) i = im1+1 if (i .gt. n) i = 1 c c denormalize tension factor c sigmap = abs(sigma)*float(n)/s(n) c c set up and perform interpolation c si = s(i) if (im1 .eq. n) si = s(n)+s(1) del1 = tn-s(im1) del2 = si-tn dels = si-s(im1) sumx = (x(i)*del1+x(im1)*del2)/dels sumy = (y(i)*del1+y(im1)*del2)/dels sumxt = s(n)*(x(i)-x(im1))/dels sumyt = s(n)*(y(i)-y(im1))/dels if (sigmap .ne. 0.) go to 1 dels6 = 6.*dels d = del1*del2/dels6 c1 = -(del1+dels)*d c2 = -(del2+dels)*d dels6 = dels6/s(n) ct1 = (2.*del1*del1-del2*(del1+dels))/dels6 ct2 = -(2.*del2*del2-del1*(del2+dels))/dels6 dels = dels/(s(n)*s(n)) ctt1 = del1/dels ctt2 = del2/dels go to 2 1 sigdel = sigmap*dels call snhcsh (ss,dummy,sigdel,-1) call snhcsh (s1,co1,sigmap*del1,0) call snhcsh (s2,co2,sigmap*del2,0) d = sigdel*sigmap*(1.+ss) c1 = del1*(s1-ss)/d c2 = del2*(s2-ss)/d ct1 = (co1-ss)*s(n)/d ct2 = -(co2-ss)*s(n)/d ctt1 = del1*(1.+s1)*s(n)*s(n)/(dels*(1.+ss)) ctt2 = del2*(1.+s2)*s(n)*s(n)/(dels*(1.+ss)) 2 xs = sumx+c1*xp(i)+c2*xp(im1) ys = sumy+c1*yp(i)+c2*yp(im1) xst = sumxt+ct1*xp(i)+ct2*xp(im1) yst = sumyt+ct1*yp(i)+ct2*yp(im1) xstt = ctt1*xp(i)+ctt2*xp(im1) ystt = ctt1*yp(i)+ctt2*yp(im1) return end subroutine surf1 (m,n,x,y,z,iz,zx1,zxm,zy1,zyn,zxy11, * zxym1,zxy1n,zxymn,islpsw,zp,temp, * sigma,ierr) c integer m,n,iz,islpsw,ierr real x(m),y(n),z(iz,n),zx1(n),zxm(n),zy1(m),zyn(m), * zxy11,zxym1,zxy1n,zxymn,zp(m,n,3),temp(1),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine determines the parameters necessary to c compute an interpolatory surface passing through a rect- c angular grid of functional values. the surface determined c can be represented as the tensor product of splines under c tension. the x- and y-partial derivatives around the c boundary and the x-y-partial derivatives at the four c corners may be specified or omitted. for actual mapping c of points onto the surface it is necessary to call the c function surf2. c c on input-- c c m is the number of grid lines in the x-direction, i. e. c lines parallel to the y-axis (m .ge. 2). c c n is the number of grid lines in the y-direction, i. e. c lines parallel to the x-axis (n .ge. 2). c c x is an array of the m x-coordinates of the grid lines c in the x-direction. these should be strictly increasing. c c y is an array of the n y-coordinates of the grid lines c in the y-direction. these should be strictly increasing. c c z is an array of the m * n functional values at the grid c points, i. e. z(i,j) contains the functional value at c (x(i),y(j)) for i = 1,...,m and j = 1,...,n. c c iz is the row dimension of the matrix z used in the c calling program (iz .ge. m). c c zx1 and zxm are arrays of the m x-partial derivatives c of the function along the x(1) and x(m) grid lines, c respectively. thus zx1(j) and zxm(j) contain the x-part- c ial derivatives at the points (x(1),y(j)) and c (x(m),y(j)), respectively, for j = 1,...,n. either of c these parameters will be ignored (and approximations c supplied internally) if islpsw so indicates. c c zy1 and zyn are arrays of the n y-partial derivatives c of the function along the y(1) and y(n) grid lines, c respectively. thus zy1(i) and zyn(i) contain the y-part- c ial derivatives at the points (x(i),y(1)) and c (x(i),y(n)), respectively, for i = 1,...,m. either of c these parameters will be ignored (and estimations c supplied internally) if islpsw so indicates. c c zxy11, zxym1, zxy1n, and zxymn are the x-y-partial c derivatives of the function at the four corners, c (x(1),y(1)), (x(m),y(1)), (x(1),y(n)), and (x(m),y(n)), c respectively. any of the parameters will be ignored (and c estimations supplied internally) if islpsw so indicates. c c islpsw contains a switch indicating which boundary c derivative information is user-supplied and which c should be estimated by this subroutine. to determine c islpsw, let c i1 = 0 if zx1 is user-supplied (and = 1 otherwise), c i2 = 0 if zxm is user-supplied (and = 1 otherwise), c i3 = 0 if zy1 is user-supplied (and = 1 otherwise), c i4 = 0 if zyn is user-supplied (and = 1 otherwise), c i5 = 0 if zxy11 is user-supplied c (and = 1 otherwise), c i6 = 0 if zxym1 is user-supplied c (and = 1 otherwise), c i7 = 0 if zxy1n is user-supplied c (and = 1 otherwise), c i8 = 0 if zxymn is user-supplied c (and = 1 otherwise), c then islpsw = i1 + 2*i2 + 4*i3 + 8*i4 + 16*i5 + 32*i6 c + 64*i7 + 128*i8 c thus islpsw = 0 indicates all derivative information is c user-supplied and islpsw = 255 indicates no derivative c information is user-supplied. any value between these c limits is valid. c c zp is an array of at least 3*m*n locations. c c temp is an array of at least n+n+m locations which is c used for scratch storage. c c and c c sigma contains the tension factor. this value indicates c the curviness desired. if abs(sigma) is nearly zero c (e. g. .001) the resulting surface is approximately the c tensor product of cubic splines. if abs(sigma) is large c (e. g. 50.) the resulting surface is approximately c bi-linear. if sigma equals zero tensor products of c cubic splines result. a standard value for sigma is c approximately 1. in absolute value. c c on output-- c c zp contains the values of the xx-, yy-, and xxyy-partial c derivatives of the surface at the given nodes. c c ierr contains an error flag, c = 0 for normal return, c = 1 if n is less than 2 or m is less than 2, c = 2 if the x-values or y-values are not strictly c increasing. c c and c c m, n, x, y, z, iz, zx1, zxm, zy1, zyn, zxy11, zxym1, c zxy1n, zxymn, islpsw, and sigma are unaltered. c c this subroutine references package modules ceez, terms, c and snhcsh. c c----------------------------------------------------------- c mm1 = m-1 mp1 = m+1 nm1 = n-1 np1 = n+1 npm = n+m ierr = 0 if (n .le. 1 .or. m .le. 1) go to 46 if (y(n) .le. y(1)) go to 47 c c denormalize tension factor in y-direction c sigmay = abs(sigma)*float(n-1)/(y(n)-y(1)) c c obtain y-partial derivatives along y = y(1) c if ((islpsw/8)*2 .ne. (islpsw/4)) go to 2 do 1 i = 1,m 1 zp(i,1,1) = zy1(i) go to 5 2 dely1 = y(2)-y(1) dely2 = dely1+dely1 if (n .gt. 2) dely2 = y(3)-y(1) if (dely1 .le. 0. .or. dely2 .le. dely1) go to 47 call ceez (dely1,dely2,sigmay,c1,c2,c3,n) do 3 i = 1,m 3 zp(i,1,1) = c1*z(i,1)+c2*z(i,2) if (n .eq. 2) go to 5 do 4 i = 1,m 4 zp(i,1,1) = zp(i,1,1)+c3*z(i,3) c c obtain y-partial derivatives along y = y(n) c 5 if ((islpsw/16)*2 .ne. (islpsw/8)) go to 7 do 6 i = 1,m npi = n+i 6 temp(npi) = zyn(i) go to 10 7 delyn = y(n)-y(nm1) delynm = delyn+delyn if (n .gt. 2) delynm = y(n)-y(n-2) if (delyn .le. 0. .or. delynm .le. delyn) go to 47 call ceez (-delyn,-delynm,sigmay,c1,c2,c3,n) do 8 i = 1,m npi = n+i 8 temp(npi) = c1*z(i,n)+c2*z(i,nm1) if (n .eq. 2) go to 10 do 9 i = 1,m npi = n+i 9 temp(npi) = temp(npi)+c3*z(i,n-2) 10 if (x(m) .le. x(1)) go to 47 c c denormalize tension factor in x-direction c sigmax = abs(sigma)*float(m-1)/(x(m)-x(1)) c c obtain x-partial derivatives along x = x(1) c if ((islpsw/2)*2 .ne. islpsw) go to 12 do 11 j = 1,n 11 zp(1,j,2) = zx1(j) if ((islpsw/32)*2 .eq. (islpsw/16) .and. * (islpsw/128)*2 .eq. (islpsw/64)) go to 15 12 delx1 = x(2)-x(1) delx2 = delx1+delx1 if (m .gt. 2) delx2 = x(3)-x(1) if (delx1 .le. 0. .or. delx2 .le. delx1) go to 47 call ceez (delx1,delx2,sigmax,c1,c2,c3,m) if ((islpsw/2)*2 .eq. islpsw) go to 15 do 13 j = 1,n 13 zp(1,j,2) = c1*z(1,j)+c2*z(2,j) if (m .eq. 2) go to 15 do 14 j = 1,n 14 zp(1,j,2) = zp(1,j,2)+c3*z(3,j) c c obtain x-y-partial derivative at (x(1),y(1)) c 15 if ((islpsw/32)*2 .ne. (islpsw/16)) go to 16 zp(1,1,3) = zxy11 go to 17 16 zp(1,1,3) = c1*zp(1,1,1)+c2*zp(2,1,1) if (m .gt. 2) zp(1,1,3) = zp(1,1,3)+c3*zp(3,1,1) c c obtain x-y-partial derivative at (x(1),y(n)) c 17 if ((islpsw/128)*2 .ne. (islpsw/64)) go to 18 zxy1ns = zxy1n go to 19 18 zxy1ns = c1*temp(n+1)+c2*temp(n+2) if (m .gt. 2) zxy1ns = zxy1ns+c3*temp(n+3) c c obtain x-partial derivative along x = x(m) c 19 if ((islpsw/4)*2 .ne. (islpsw/2)) go to 21 do 20 j = 1,n npmpj = npm+j 20 temp(npmpj) = zxm(j) if ((islpsw/64)*2 .eq. (islpsw/32) .and. * (islpsw/256)*2 .eq. (islpsw/128)) go to 24 21 delxm = x(m)-x(mm1) delxmm = delxm+delxm if (m .gt. 2) delxmm = x(m)-x(m-2) if (delxm .le. 0. .or. delxmm .le. delxm) go to 47 call ceez (-delxm,-delxmm,sigmax,c1,c2,c3,m) if ((islpsw/4)*2 .eq. (islpsw/2)) go to 24 do 22 j = 1,n npmpj = npm+j 22 temp(npmpj) = c1*z(m,j)+c2*z(mm1,j) if (m .eq. 2) go to 24 do 23 j = 1,n npmpj = npm+j 23 temp(npmpj) = temp(npmpj)+c3*z(m-2,j) c c obtain x-y-partial derivative at (x(m),y(1)) c 24 if ((islpsw/64)*2 .ne. (islpsw/32)) go to 25 zp(m,1,3) = zxym1 go to 26 25 zp(m,1,3) = c1*zp(m,1,1)+c2*zp(mm1,1,1) if (m .gt. 2) zp(m,1,3) = zp(m,1,3)+c3*zp(m-2,1,1) c c obtain x-y-partial derivative at (x(m),y(n)) c 26 if ((islpsw/256)*2 .ne. (islpsw/128)) go to 27 zxymns = zxymn go to 28 27 zxymns = c1*temp(npm)+c2*temp(npm-1) if (m .gt. 2) zxymns = zxymns+c3*temp(npm-2) c c set up right hand sides and tridiagonal system for y-grid c perform forward elimination c 28 del1 = y(2)-y(1) if (del1 .le. 0.) go to 47 deli = 1./del1 do 29 i = 1,m 29 zp(i,2,1) = deli*(z(i,2)-z(i,1)) zp(1,2,3) = deli*(zp(1,2,2)-zp(1,1,2)) zp(m,2,3) = deli*(temp(npm+2)-temp(npm+1)) call terms (diag1,sdiag1,sigmay,del1) diagi = 1./diag1 do 30 i = 1,m 30 zp(i,1,1) = diagi*(zp(i,2,1)-zp(i,1,1)) zp(1,1,3) = diagi*(zp(1,2,3)-zp(1,1,3)) zp(m,1,3) = diagi*(zp(m,2,3)-zp(m,1,3)) temp(1) = diagi*sdiag1 if (n .eq. 2) go to 34 do 33 j = 2,nm1 jm1 = j-1 jp1 = j+1 npmpj = npm+j del2 = y(jp1)-y(j) if (del2 .le. 0.) go to 47 deli = 1./del2 do 31 i = 1,m 31 zp(i,jp1,1) = deli*(z(i,jp1)-z(i,j)) zp(1,jp1,3) = deli*(zp(1,jp1,2)-zp(1,j,2)) zp(m,jp1,3) = deli*(temp(npmpj+1)-temp(npmpj)) call terms (diag2,sdiag2,sigmay,del2) diagin = 1./(diag1+diag2-sdiag1*temp(jm1)) do 32 i = 1,m 32 zp(i,j,1) = diagin*(zp(i,jp1,1)-zp(i,j,1)- * sdiag1*zp(i,jm1,1)) zp(1,j,3) = diagin*(zp(1,jp1,3)-zp(1,j,3)- * sdiag1*zp(1,jm1,3)) zp(m,j,3) = diagin*(zp(m,jp1,3)-zp(m,j,3)- * sdiag1*zp(m,jm1,3)) temp(j) = diagin*sdiag2 diag1 = diag2 33 sdiag1 = sdiag2 34 diagin = 1./(diag1-sdiag1*temp(nm1)) do 35 i = 1,m npi = n+i 35 zp(i,n,1) = diagin*(temp(npi)-zp(i,n,1)- * sdiag1*zp(i,nm1,1)) zp(1,n,3) = diagin*(zxy1ns-zp(1,n,3)- * sdiag1*zp(1,nm1,3)) temp(n) = diagin*(zxymns-zp(m,n,3)- * sdiag1*zp(m,nm1,3)) c c perform back substitution c do 37 j = 2,n jbak = np1-j jbakp1 = jbak+1 t = temp(jbak) do 36 i = 1,m 36 zp(i,jbak,1) = zp(i,jbak,1)-t*zp(i,jbakp1,1) zp(1,jbak,3) = zp(1,jbak,3)-t*zp(1,jbakp1,3) 37 temp(jbak) = zp(m,jbak,3)-t*temp(jbakp1) c c set up right hand sides and tridiagonal system for x-grid c perform forward elimination c del1 = x(2)-x(1) if (del1 .le. 0.) go to 47 deli = 1./del1 do 38 j = 1,n zp(2,j,2) = deli*(z(2,j)-z(1,j)) 38 zp(2,j,3) = deli*(zp(2,j,1)-zp(1,j,1)) call terms (diag1,sdiag1,sigmax,del1) diagi = 1./diag1 do 39 j = 1,n zp(1,j,2) = diagi*(zp(2,j,2)-zp(1,j,2)) 39 zp(1,j,3) = diagi*(zp(2,j,3)-zp(1,j,3)) temp(n+1) = diagi*sdiag1 if (m .eq. 2) go to 43 do 42 i = 2,mm1 im1 = i-1 ip1 = i+1 npi = n+i del2 = x(ip1)-x(i) if (del2 .le. 0.) go to 47 deli = 1./del2 do 40 j = 1,n zp(ip1,j,2) = deli*(z(ip1,j)-z(i,j)) 40 zp(ip1,j,3) = deli*(zp(ip1,j,1)-zp(i,j,1)) call terms (diag2,sdiag2,sigmax,del2) diagin = 1./(diag1+diag2-sdiag1*temp(npi-1)) do 41 j = 1,n zp(i,j,2) = diagin*(zp(ip1,j,2)-zp(i,j,2)- * sdiag1*zp(im1,j,2)) 41 zp(i,j,3) = diagin*(zp(ip1,j,3)-zp(i,j,3)- * sdiag1*zp(im1,j,3)) temp(npi) = diagin*sdiag2 diag1 = diag2 42 sdiag1 = sdiag2 43 diagin = 1./(diag1-sdiag1*temp(npm-1)) do 44 j = 1,n npmpj = npm+j zp(m,j,2) = diagin*(temp(npmpj)-zp(m,j,2)- * sdiag1*zp(mm1,j,2)) 44 zp(m,j,3) = diagin*(temp(j)-zp(m,j,3)- * sdiag1*zp(mm1,j,3)) c c perform back substitution c do 45 i = 2,m ibak = mp1-i ibakp1 = ibak+1 npibak = n+ibak t = temp(npibak) do 45 j = 1,n zp(ibak,j,2) = zp(ibak,j,2)-t*zp(ibakp1,j,2) 45 zp(ibak,j,3) = zp(ibak,j,3)-t*zp(ibakp1,j,3) return c c too few points c 46 ierr = 1 return c c points not strictly increasing c 47 ierr = 2 return end function surf2 (xx,yy,m,n,x,y,z,iz,zp,sigma) c integer m,n,iz real xx,yy,x(m),y(n),z(iz,n),zp(m,n,3),sigma c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this function interpolates a surface at a given coordinate c pair using a bi-spline under tension. the subroutine surf1 c should be called earlier to determine certain necessary c parameters. c c on input-- c c xx and yy contain the x- and y-coordinates of the point c to be mapped onto the interpolating surface. c c m and n contain the number of grid lines in the x- and c y-directions, respectively, of the rectangular grid c which specified the surface. c c x and y are arrays containing the x- and y-grid values, c respectively, each in increasing order. c c z is a matrix containing the m * n functional values c corresponding to the grid values (i. e. z(i,j) is the c surface value at the point (x(i),y(j)) for i = 1,...,m c and j = 1,...,n). c c iz contains the row dimension of the array z as declared c in the calling program. c c zp is an array of 3*m*n locations stored with the c various surface derivative information determined by c surf1. c c and c c sigma contains the tension factor (its sign is ignored). c c the parameters m, n, x, y, z, iz, zp, and sigma should be c input unaltered from the output of surf1. c c on output-- c c surf2 contains the interpolated surface value. c c none of the input parameters are altered. c c this function references package modules intrvl and c snhcsh. c c----------------------------------------------------------- c c inline one dimensional cubic spline interpolation c hermz (f1,f2,fp1,fp2) = (f2*del1+f1*del2)/dels-del1* * del2*(fp2*(del1+dels)+ * fp1*(del2+dels))/ * (6.*dels) c c inline one dimensional spline under tension interpolation c hermnz (f1,f2,fp1,fp2,sigmap) = (f2*del1+f1*del2)/dels * +(fp2*del1*(sinhm1-sinhms) * +fp1*del2*(sinhm2-sinhms) * )/(sigmap*sigmap*dels*(1.+sinhms)) c c denormalize tension factor in x and y direction c sigmax = abs(sigma)*float(m-1)/(x(m)-x(1)) sigmay = abs(sigma)*float(n-1)/(y(n)-y(1)) c c determine y interval c jm1 = intrvl (yy,y,n) j = jm1+1 c c determine x interval c im1 = intrvl (xx,x,m) i = im1+1 del1 = yy-y(jm1) del2 = y(j)-yy dels = y(j)-y(jm1) if (sigmay .ne. 0.) go to 1 c c perform four interpolations in y-direction c zim1 = hermz(z(i-1,j-1),z(i-1,j),zp(i-1,j-1,1), * zp(i-1,j,1)) zi = hermz(z(i,j-1),z(i,j),zp(i,j-1,1),zp(i,j,1)) zxxim1 = hermz(zp(i-1,j-1,2),zp(i-1,j,2), * zp(i-1,j-1,3),zp(i-1,j,3)) zxxi = hermz(zp(i,j-1,2),zp(i,j,2), * zp(i,j-1,3),zp(i,j,3)) go to 2 1 call snhcsh (sinhm1,dummy,sigmay*del1,-1) call snhcsh (sinhm2,dummy,sigmay*del2,-1) call snhcsh (sinhms,dummy,sigmay*dels,-1) zim1 = hermnz(z(i-1,j-1),z(i-1,j),zp(i-1,j-1,1), * zp(i-1,j,1),sigmay) zi = hermnz(z(i,j-1),z(i,j),zp(i,j-1,1),zp(i,j,1), * sigmay) zxxim1 = hermnz(zp(i-1,j-1,2),zp(i-1,j,2), * zp(i-1,j-1,3),zp(i-1,j,3),sigmay) zxxi = hermnz(zp(i,j-1,2),zp(i,j,2), * zp(i,j-1,3),zp(i,j,3),sigmay) c c perform final interpolation in x-direction c 2 del1 = xx-x(im1) del2 = x(i)-xx dels = x(i)-x(im1) if (sigmax .ne. 0.) go to 3 surf2 = hermz(zim1,zi,zxxim1,zxxi) return 3 call snhcsh (sinhm1,dummy,sigmax*del1,-1) call snhcsh (sinhm2,dummy,sigmax*del2,-1) call snhcsh (sinhms,dummy,sigmax*dels,-1) surf2 = hermnz(zim1,zi,zxxim1,zxxi,sigmax) return end subroutine ceez (del1,del2,sigma,c1,c2,c3,n) c real del1,del2,sigma,c1,c2,c3 c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine determines the coefficients c1, c2, and c3 c used to determine endpoint slopes. specifically, if c function values y1, y2, and y3 are given at points x1, x2, c and x3, respectively, the quantity c1*y1 + c2*y2 + c3*y3 c is the value of the derivative at x1 of a spline under c tension (with tension factor sigma) passing through the c three points and having third derivative equal to zero at c x1. optionally, only two values, c1 and c2 are determined. c c on input-- c c del1 is x2-x1 (.gt. 0.). c c del2 is x3-x1 (.gt. 0.). if n .eq. 2, this parameter is c ignored. c c sigma is the tension factor. c c and c c n is a switch indicating the number of coefficients to c be returned. if n .eq. 2 only two coefficients are c returned. otherwise all three are returned. c c on output-- c c c1, c2, and c3 contain the coefficients. c c none of the input parameters are altered. c c this subroutine references package module snhcsh. c c----------------------------------------------------------- c if (n .eq. 2) go to 2 if (sigma .ne. 0.) go to 1 del = del2-del1 c c tension .eq. 0. c c1 = -(del1+del2)/(del1*del2) c2 = del2/(del1*del) c3 = -del1/(del2*del) return c c tension .ne. 0. c 1 call snhcsh (dummy,coshm1,sigma*del1,1) call snhcsh (dummy,coshm2,sigma*del2,1) delp = sigma*(del2+del1)/2. delm = sigma*(del2-del1)/2. call snhcsh (sinhmp,dummy,delp,-1) call snhcsh (sinhmm,dummy,delm,-1) denom = coshm1*(del2-del1)-2.*del1*delp*delm* * (1.+sinhmp)*(1.+sinhmm) c1 = 2.*delp*delm*(1.+sinhmp)*(1.+sinhmm)/denom c2 = -coshm2/denom c3 = coshm1/denom return c c two coefficients c 2 c1 = -1./del1 c2 = -c1 return end subroutine curvpp (n,x,y,p,d,isw,s,eps,ys,ysp,sigma, * td,tsd1,hd,hsd1,hsd2,rd,rsd1,rsd2, * rnm1,rn,v,ierr) c integer n,isw,ierr real x(n),y(n),p,d(n),s,eps,ys(n),ysp(n),sigma,td(n), * tsd1(n),hd(n),hsd1(n),hsd2(n),rd(n),rsd1(n), * rsd2(n),rnm1(n),rn(n),v(n) c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine determines the parameters necessary to c compute a periodic smoothing spline under tension. for a c given increasing sequence of abscissae (x(i)), i = 1,...,n c and associated ordinates (y(i)), i = 1,...,n, letting p be c the period, x(n+1) = x(1)+p, and y(n+1) = y(1), the c function determined minimizes the summation from i = 1 to c n of the square of the second derivative of f plus sigma c squared times the difference of the first derivative of f c and (f(x(i+1))-f(x(i)))/(x(i+1)-x(i)) squared, over all c functions f with period p and two continuous derivatives c such that the summation of the square of c (f(x(i))-y(i))/d(i) is less than or equal to a given c constant s, where (d(i)), i = 1,...,n are a given set of c observation weights. the function determined is a periodic c spline under tension with third derivative discontinuities c at (x(i)) i = 1,...,n (and all periodic translations of c these values). for actual computation of points on the c curve it is necessary to call the function curvp2. c c on input-- c c n is the number of values to be smoothed (n.ge.2). c c x is an array of the n increasing abscissae of the c values to be smoothed. c c y is an array of the n ordinates of the values to be c smoothed, (i. e. y(k) is the functional value c corresponding to x(k) ). c c p is the period (p .gt. x(n)-x(1)). c c d is a parameter containing the observation weights. c this may either be an array of length n or a scalar c (interpreted as a constant). the value of d c corresponding to the observation (x(k),y(k)) should c be an approximation to the standard deviation of error. c c isw contains a switch indicating whether the parameter c d is to be considered a vector or a scalar, c = 0 if d is an array of length n, c = 1 if d is a scalar. c c s contains the value controlling the smoothing. this c must be non-negative. for s equal to zero, the c subroutine does interpolation, larger values lead to c smoother funtions. if parameter d contains standard c deviation estimates, a reasonable value for s is c float(n). c c eps contains a tolerance on the relative precision to c which s is to be interpreted. this must be greater than c or equal to zero and less than equal or equal to one. a c reasonable value for eps is sqrt(2./float(n)). c c ys is an array of length at least n. c c ysp is an array of length at least n. c c sigma contains the tension factor. this value indicates c the degree to which the first derivative part of the c smoothing functional is emphasized. if sigma is nearly c zero (e. g. .001) the resulting curve is approximately a c cubic spline. if sigma is large (e. g. 50.) the c resulting curve is nearly a polygonal line. if sigma c equals zero a cubic spline results. a standard value for c sigma is approximately 1. c c and c c td, tsd1, hd, hsd1, hsd2, rd, rsd1, rsd2, rnm1, rn, and c v are arrays of length at least n which are used for c scratch storage. c c on output-- c c ys contains the smoothed ordinate values. c c ysp contains the values of the second derivative of the c smoothed curve at the given nodes. c c ierr contains an error flag, c = 0 for normal return, c = 1 if n is less than 2, c = 2 if s is negative, c = 3 if eps is negative or greater than one, c = 4 if x-values are not strictly increasing, c = 5 if a d-value is non-positive, c = 6 if p is less than or equal to x(n)-x(1). c c and c c n, x, y, d, isw, s, eps, and sigma are unaltered. c c this subroutine references package modules terms and c snhcsh. c c----------------------------------------------------------- c if (n .lt. 2) go to 25 if (s .lt. 0.) go to 26 if (eps .lt. 0. .or. eps .gt. 1.) go to 27 if (p .le. x(n)-x(1)) go to 30 ierr = 0 q = 0. rsd1(1) = 0. rsd2(1) = 0. rsd2(2) = 0. rsd1(n-1) = 0. rsd2(n-1) = 0. rsd2(n) = 0. c c denormalize tension factor c sigmap = abs(sigma)*float(n)/p c c form t matrix and second differences of y into ys c nm1 = n-1 nm2 = n-2 nm3 = n-3 delxi1 = x(1)+p-x(n) delyi1 = (y(1)-y(n))/delxi1 call terms (dim1,tsd1(1),sigmap,delxi1) hsd1(1) = 1./delxi1 do 1 i = 1,n ip1 = i+1 if (i .eq. n) ip1 = 1 delxi = x(ip1)-x(i) if (i .eq. n) delxi = x(1)+p-x(n) if (delxi .le. 0.) go to 28 delyi = (y(ip1)-y(i))/delxi ys(i) = delyi-delyi1 call terms (di,tsd1(ip1),sigmap,delxi) td(i) = di+dim1 hd(i) = -(1./delxi+1./delxi1) hsd1(ip1) = 1./delxi delxi1 = delxi delyi1 = delyi 1 dim1 = di hsd11 = hsd1(1) if (n .ge. 3) go to 2 tsd1(2) = tsd1(1)+tsd1(2) tsd1(1) = 0. hsd1(2) = hsd1(1)+hsd1(2) hsd1(1) = 0. c c calculate lower and upper tolerances c 2 sl = s*(1.-eps) su = s*(1.+eps) if (d(1) .le. 0.) go to 29 if (isw .eq. 1) go to 5 c c form h matrix - d array c betapp = hsd1(n)*d(n)*d(n) betap = hsd1(1)*d(1)*d(1) alphap = hd(n)*d(n)*d(n) im1 = n sumd = 0. sumy = 0. do 3 i = 1,n disq = d(i)*d(i) sumd = sumd+1./disq sumy = sumy+y(i)/disq ip1 = i+1 if (i .eq. n) ip1 = 1 alpha = hd(i)*disq if (d(ip1) .le. 0.) go to 29 hsd1ip = hsd1(ip1) if (i .eq. n) hsd1ip = hsd11 beta = hsd1ip*d(ip1)*d(ip1) hd(i) = (hsd1(i)*d(im1))**2+alpha*hd(i) * +beta*hsd1ip hsd2(i) = hsd1(i)*betapp hsd1(i) = hsd1(i)*(alpha+alphap) im1 = i alphap = alpha betapp = betap 3 betap = beta if (n .eq. 3) hsd1(3) = hsd1(3)+hsd2(2) c c test for straight line fit c con = sumy/sumd sum = 0. do 4 i = 1,n 4 sum = sum+((y(i)-con)/d(i))**2 if (sum .le. su) go to 23 go to 8 c c form h matrix - d constant c 5 sl = d(1)*d(1)*sl su = d(1)*d(1)*su hsd1p = hsd1(n) hdim1 = hd(n) sumy = 0. do 6 i = 1,n sumy = sumy+y(i) hsd1ip = hsd11 if (i .lt. n) hsd1ip = hsd1(i+1) hdi = hd(i) hd(i) = hsd1(i)*hsd1(i)+hdi*hdi+hsd1ip*hsd1ip hsd2(i) = hsd1(i)*hsd1p hsd1p = hsd1(i) hsd1(i) = hsd1p*(hdi+hdim1) 6 hdim1 = hdi if (n .eq. 3) hsd1(3) = hsd1(3)+hsd2(2) c c test for straight line fit c con = sumy/float(n) sum = 0. do 7 i = 1,n 7 sum = sum+(y(i)-con)**2 if (sum .le. su) go to 23 c c top of iteration c cholesky factorization of q*t+h into r c c c i = 1 c 8 rd(1) = 1./(q*td(1)+hd(1)) rnm1(1) = hsd2(1) yspnm1 = ys(nm1) rn(1) = q*tsd1(1)+hsd1(1) yspn = ys(n) ysp(1) = ys(1) rsd1i = q*tsd1(2)+hsd1(2) rsd1(2) = rsd1i*rd(1) sumnm1 = 0. sum2 = 0. sumn = 0. if (n .eq. 3) go to 11 if (n .eq. 2) go to 12 c c i = 2 c rd(2) = 1./(q*td(2)+hd(2)-rsd1i*rsd1(2)) rnm1(2) = -rnm1(1)*rsd1(2) rn(2) = hsd2(2)-rn(1)*rsd1(2) ysp(2) = ys(2)-rsd1(2)*ysp(1) if (n .eq. 4) go to 10 do 9 i = 3,nm2 rsd2i = hsd2(i) rsd1i = q*tsd1(i)+hsd1(i)-rsd2i*rsd1(i-1) rsd2(i) = rsd2i*rd(i-2) rsd1(i) = rsd1i*rd(i-1) rd(i) = 1./(q*td(i)+hd(i)-rsd1i*rsd1(i) * -rsd2i*rsd2(i)) rnm1(i) = -rnm1(i-2)*rsd2(i)-rnm1(i-1)*rsd1(i) rnm1t = rnm1(i-2)*rd(i-2) sumnm1 = sumnm1+rnm1t*rnm1(i-2) rnm1(i-2) = rnm1t sum2 = sum2+rnm1t*rn(i-2) yspnm1 = yspnm1-rnm1t*ysp(i-2) rn(i) = -rn(i-2)*rsd2(i)-rn(i-1)*rsd1(i) rnt = rn(i-2)*rd(i-2) sumn = sumn+rnt*rn(i-2) rn(i-2) = rnt yspn = yspn-rnt*ysp(i-2) 9 ysp(i) = ys(i)-rsd1(i)*ysp(i-1)-rsd2(i)*ysp(i-2) c c i = n-3 c 10 rnm1(nm3) = hsd2(nm1)+rnm1(nm3) rnm1(nm2) = rnm1(nm2)-hsd2(nm1)*rsd1(nm2) rnm1t = rnm1(nm3)*rd(nm3) sumnm1 = sumnm1+rnm1t*rnm1(nm3) rnm1(nm3) = rnm1t sum2 = sum2+rnm1t*rn(nm3) yspnm1 = yspnm1-rnm1t*ysp(nm3) rnt = rn(nm3)*rd(nm3) sumn = sumn+rnt*rn(nm3) rn(nm3) = rnt yspn = yspn-rnt*ysp(nm3) c c i = n-2 c 11 rnm1(nm2) = q*tsd1(nm1)+hsd1(nm1)+rnm1(nm2) rnm1t = rnm1(nm2)*rd(nm2) sumnm1 = sumnm1+rnm1t*rnm1(nm2) rnm1(nm2) = rnm1t rn(nm2) = hsd2(n)+rn(nm2) sum2 = sum2+rnm1t*rn(nm2) yspnm1 = yspnm1-rnm1t*ysp(nm2) rnt = rn(nm2)*rd(nm2) sumn = sumn+rnt*rn(nm2) rn(nm2) = rnt yspn = yspn-rnt*ysp(nm2) c c i = n-1 c 12 rd(nm1) = 1./(q*td(nm1)+hd(nm1)-sumnm1) ysp(nm1) = yspnm1 rn(nm1) = q*tsd1(n)+hsd1(n)-sum2 rnt = rn(nm1)*rd(nm1) sumn = sumn+rnt*rn(nm1) rn(nm1) = rnt yspn = yspn-rnt*ysp(nm1) c c i = n c rdn = q*td(n)+hd(n)-sumn rd(n) = 0. if (rdn .gt. 0.) rd(n) = 1./rdn ysp(n) = yspn c c back solve of r(transpose)* r * ysp = ys c ysp(n) = rd(n)*ysp(n) ysp(nm1) = rd(nm1)*ysp(nm1)-rn(nm1)*ysp(n) if (n .eq. 2) go to 14 yspn = ysp(n) yspnm1 = ysp(nm1) do 13 ibak = 1,nm2 i = nm1-ibak 13 ysp(i) = rd(i)*ysp(i)-rsd1(i+1)*ysp(i+1) * -rsd2(i+2)*ysp(i+2)-rnm1(i)*yspnm1 * -rn(i)*yspn 14 sum = 0. delyi1 = (ysp(1)-ysp(n))/(x(1)+p-x(n)) if (isw .eq. 1) go to 16 c c calculation of residual norm c - d array c do 15 i = 1,nm1 delyi = (ysp(i+1)-ysp(i))/(x(i+1)-x(i)) v(i) = (delyi-delyi1)*d(i)*d(i) sum = sum+v(i)*(delyi-delyi1) 15 delyi1 = delyi delyi = (ysp(1)-ysp(n))/(x(1)+p-x(n)) v(n) = (delyi-delyi1)*d(n)*d(n) go to 18 c c calculation of residual norm c - d constant c 16 do 17 i = 1,nm1 delyi = (ysp(i+1)-ysp(i))/(x(i+1)-x(i)) v(i) = delyi-delyi1 sum = sum+v(i)*(delyi-delyi1) 17 delyi1 = delyi delyi = (ysp(1)-ysp(n))/(x(1)+p-x(n)) v(n) = delyi-delyi1 18 sum = sum+v(n)*(delyi-delyi1) c c test for convergence c if (sum .le. su .and. sum .ge. sl .and. q .gt. 0.) * go to 21 c c calculation of newton correction c f = 0. g = 0. rnm1sm = 0. rnsm = 0. im1 = n if (n .eq. 2) go to 20 wim2 = 0. wim1 = 0. do 19 i = 1,nm2 tui = tsd1(i)*ysp(im1)+td(i)*ysp(i) * +tsd1(i+1)*ysp(i+1) wi = tui-rsd1(i)*wim1-rsd2(i)*wim2 rnm1sm = rnm1sm-rnm1(i)*wi rnsm = rnsm-rn(i)*wi f = f+tui*ysp(i) g = g+wi*wi*rd(i) im1 = i wim2 = wim1 19 wim1 = wi 20 tui = tsd1(nm1)*ysp(im1)+td(nm1)*ysp(nm1) * +tsd1(n)*ysp(n) wi = tui+rnm1sm f = f+tui*ysp(nm1) g = g+wi*wi*rd(nm1) tui = tsd1(n)*ysp(nm1)+td(n)*ysp(n) * +tsd1(1)*ysp(1) wi = tui+rnsm-rn(nm1)*wi f = f+tui*ysp(n) g = g+wi*wi*rd(n) h = f-q*g if (h .le. 0. .and. q .gt. 0.) go to 21 c c update q - newton step c step = (sum-sqrt(sum*sl))/h if (sl .ne. 0.) step = step*sqrt(sum/sl) q = q+step go to 8 c c store smoothed y-values and second derivatives c 21 do 22 i = 1,n ys(i) = y(i)-v(i) 22 ysp(i) = q*ysp(i) return c c store constant ys and zero ysp c 23 do 24 i = 1,n ys(i) = con 24 ysp(i) = 0. return c c n less than 2 c 25 ierr = 1 return c c s negative c 26 ierr = 2 return c c eps negative or greater than 1 c 27 ierr = 3 return c c x-values not strictly increasing c 28 ierr = 4 return c c weight non-positive c 29 ierr = 5 return c c incorrect period c 30 ierr = 6 return end subroutine curvss (n,x,y,d,isw,s,eps,ys,ysp,sigma,td, * tsd1,hd,hsd1,hsd2,rd,rsd1,rsd2,v, * ierr) c integer n,isw,ierr real x(n),y(n),d(n),s,eps,ys(n),ysp(n),sigma,td(n), * tsd1(n),hd(n),hsd1(n),hsd2(n),rd(n),rsd1(n), * rsd2(n),v(n) c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine determines the parameters necessary to c compute a smoothing spline under tension. for a given c increasing sequence of abscissae (x(i)), i = 1,..., n and c associated ordinates (y(i)), i = 1,..., n, the function c determined minimizes the summation from i = 1 to n-1 of c the square of the second derivative of f plus sigma c squared times the difference of the first derivative of f c and (f(x(i+1))-f(x(i)))/(x(i+1)-x(i)) squared, over all c functions f with two continuous derivatives such that the c summation of the square of (f(x(i))-y(i))/d(i) is less c than or equal to a given constant s, where (d(i)), i = 1, c ..., n are a given set of observation weights. the c function determined is a spline under tension with third c derivative discontinuities at (x(i)), i = 2,..., n-1. for c actual computation of points on the curve it is necessary c to call the function curv2. c c on input-- c c n is the number of values to be smoothed (n.ge.2). c c x is an array of the n increasing abscissae of the c values to be smoothed. c c y is an array of the n ordinates of the values to be c smoothed, (i. e. y(k) is the functional value c corresponding to x(k) ). c c d is a parameter containing the observation weights. c this may either be an array of length n or a scalar c (interpreted as a constant). the value of d c corresponding to the observation (x(k),y(k)) should c be an approximation to the standard deviation of error. c c isw contains a switch indicating whether the parameter c d is to be considered a vector or a scalar, c = 0 if d is an array of length n, c = 1 if d is a scalar. c c s contains the value controlling the smoothing. this c must be non-negative. for s equal to zero, the c subroutine does interpolation, larger values lead to c smoother funtions. if parameter d contains standard c deviation estimates, a reasonable value for s is c float(n). c c eps contains a tolerance on the relative precision to c which s is to be interpreted. this must be greater than c or equal to zero and less than equal or equal to one. a c reasonable value for eps is sqrt(2./float(n)). c c ys is an array of length at least n. c c ysp is an array of length at least n. c c sigma contains the tension factor. this value indicates c the degree to which the first derivative part of the c smoothing functional is emphasized. if sigma is nearly c zero (e. g. .001) the resulting curve is approximately a c cubic spline. if sigma is large (e. g. 50.) the c resulting curve is nearly a polygonal line. if sigma c equals zero a cubic spline results. a standard value for c sigma is approximately 1. c c and c c td, tsd1, hd, hsd1, hsd2, rd, rsd1, rsd2, and v are c arrays of length at least n which are used for scratch c storage. c c on output-- c c ys contains the smoothed ordinate values. c c ysp contains the values of the second derivative of the c smoothed curve at the given nodes. c c ierr contains an error flag, c = 0 for normal return, c = 1 if n is less than 2, c = 2 if s is negative, c = 3 if eps is negative or greater than one, c = 4 if x-values are not strictly increasing, c = 5 if a d-value is non-positive. c c and c c n, x, y, d, isw, s, eps, and sigma are unaltered. c c this subroutine references package modules terms and c snhcsh. c c----------------------------------------------------------- c if (n .lt. 2) go to 16 if (s .lt. 0.) go to 17 if (eps .lt. 0. .or. eps .gt. 1.) go to 18 ierr = 0 p = 0. v(1) = 0. v(n) = 0. ysp(1) = 0. ysp(n) = 0. if (n .eq. 2) go to 14 rsd1(1) = 0. rd(1) = 0. rsd2(n) = 0. rdim1 = 0. yspim2 = 0. c c denormalize tension factor c sigmap = abs(sigma)*float(n-1)/(x(n)-x(1)) c c form t matrix and second differences of y into ys c nm1 = n-1 nm3 = n-3 delxi1 = 1. delyi1 = 0. dim1 = 0. do 1 i = 1,nm1 delxi = x(i+1)-x(i) if (delxi .le. 0.) go to 19 delyi = (y(i+1)-y(i))/delxi ys(i) = delyi-delyi1 call terms (di,tsd1(i+1),sigmap,delxi) td(i) = di+dim1 hd(i) = -(1./delxi+1./delxi1) hsd1(i+1) = 1./delxi delxi1 = delxi delyi1 = delyi 1 dim1 = di c c calculate lower and upper tolerances c sl = s*(1.-eps) su = s*(1.+eps) if (isw .eq. 1) go to 3 c c form h matrix - d array c if (d(1) .le. 0. .or. d(2) .le. 0.) go to 20 betapp = 0. betap = 0. alphap = 0. do 2 i = 2,nm1 alpha = hd(i)*d(i)*d(i) if (d(i+1) .le. 0.) go to 20 beta = hsd1(i+1)*d(i+1)*d(i+1) hd(i) = (hsd1(i)*d(i-1))**2+alpha*hd(i) * +beta*hsd1(i+1) hsd2(i) = hsd1(i)*betapp hsd1(i) = hsd1(i)*(alpha+alphap) alphap = alpha betapp = betap 2 betap = beta go to 5 c c form h matrix - d constant c 3 if (d(1) .le. 0.) go to 20 sl = d(1)*d(1)*sl su = d(1)*d(1)*su hsd1p = 0. hdim1 = 0. do 4 i = 2,nm1 hdi = hd(i) hd(i) = hsd1(i)*hsd1(i)+hdi*hdi+hsd1(i+1)*hsd1(i+1) hsd2(i) = hsd1(i)*hsd1p hsd1p = hsd1(i) hsd1(i) = hsd1p*(hdi+hdim1) 4 hdim1 = hdi c c top of iteration c cholesky factorization of p*t+h into r c 5 do 6 i = 2,nm1 rsd2i = hsd2(i) rsd1i = p*tsd1(i)+hsd1(i)-rsd2i*rsd1(i-1) rsd2(i) = rsd2i*rdim1 rdim1 = rd(i-1) rsd1(i) = rsd1i*rdim1 rd(i) = 1./(p*td(i)+hd(i)-rsd1i*rsd1(i) * -rsd2i*rsd2(i)) ysp(i) = ys(i)-rsd1(i)*ysp(i-1)-rsd2(i)*yspim2 6 yspim2 = ysp(i-1) c c back solve of r(transpose)* r * ysp = ys c ysp(nm1) = rd(nm1)*ysp(nm1) if (n .eq. 3) go to 8 do 7 ibak = 1,nm3 i = nm1-ibak 7 ysp(i) = rd(i)*ysp(i)-rsd1(i+1)*ysp(i+1) * -rsd2(i+2)*ysp(i+2) 8 sum = 0. delyi1 = 0. if (isw .eq. 1) go to 10 c c calculation of residual norm c - d array c do 9 i = 1,nm1 delyi = (ysp(i+1)-ysp(i))/(x(i+1)-x(i)) v(i) = (delyi-delyi1)*d(i)*d(i) sum = sum+v(i)*(delyi-delyi1) 9 delyi1 = delyi v(n) = -delyi1*d(n)*d(n) go to 12 c c calculation of residual norm c - d constant c 10 do 11 i = 1,nm1 delyi = (ysp(i+1)-ysp(i))/(x(i+1)-x(i)) v(i) = delyi-delyi1 sum = sum+v(i)*(delyi-delyi1) 11 delyi1 = delyi v(n) = -delyi1 12 sum = sum-v(n)*delyi1 c c test for convergence c if (sum .le. su) go to 14 c c calculation of newton correction c f = 0. g = 0. wim2 = 0. wim1 = 0. do 13 i = 2,nm1 tui = tsd1(i)*ysp(i-1)+td(i)*ysp(i) * +tsd1(i+1)*ysp(i+1) wi = tui-rsd1(i)*wim1-rsd2(i)*wim2 f = f+tui*ysp(i) g = g+wi*wi*rd(i) wim2 = wim1 13 wim1 = wi h = f-p*g if (h .le. 0.) go to 14 c c update p - newton step c step = (sum-sqrt(sum*sl))/h if (sl .ne. 0.) step = step*sqrt(sum/sl) p = p+step go to 5 c c store smoothed y-values and second derivatives c 14 do 15 i = 1,n ys(i) = y(i)-v(i) 15 ysp(i) = p*ysp(i) return c c n less than 2 c 16 ierr = 1 return c c s negative c 17 ierr = 2 return c c eps negative or greater than 1 c 18 ierr = 3 return c c x-values not strictly increasing c 19 ierr = 4 return c c weight non-positive c 20 ierr = 5 return end function intrvl (t,x,n) c integer n real t,x(n) c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this function determines the index of the interval c (determined by a given increasing sequence) in which c a given value lies. c c on input-- c c t is the given value. c c x is a vector of strictly increasing values. c c and c c n is the length of x (n .ge. 2). c c on output-- c c intrvl returns an integer i such that c c i = 1 if e t .lt. x(2) , c i = n-1 if x(n-1) .le. t , c otherwise x(i) .le. t .le. x(i+1), c c none of the input parameters are altered. c c----------------------------------------------------------- c save i data i /1/ c tt = t c c check for illegal i c if (i .ge. n) i = n/2 c c check old interval and extremes c if (tt .lt. x(i)) then if (tt .le. x(2)) then i = 1 intrvl = 1 return else il = 2 ih = i end if else if (tt .le. x(i+1)) then intrvl = i return else if (tt .ge. x(n-1)) then i = n-1 intrvl = n-1 return else il = i+1 ih = n-1 end if c c binary search loop c 1 i = (il+ih)/2 if (tt .lt. x(i)) then ih = i else if (tt .gt. x(i+1)) then il = i+1 else intrvl = i return end if go to 1 end function intrvp (t,x,n,p,tp) c integer n real t,x(n),p,tp c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this function determines the index of the interval c (determined by a given increasing sequence) in which a c given value lies, after translating the value to within c the correct period. it also returns this translated value. c c on input-- c c t is the given value. c c x is a vector of strictly increasing values. c c n is the length of x (n .ge. 2). c c and c c p contains the period. c c on output-- c c tp contains a translated value of t (i. e. x(1) .le. tp, c tp .lt. x(1)+p, and tp = t + k*p for some integer k). c c intrvl returns an integer i such that c c i = 1 if tp .lt. x(2) , c i = n if x(n) .le. tp , c otherwise x(i) .le. tp .lt. x(i+1), c c none of the input parameters are altered. c c----------------------------------------------------------- c save i data i /1/ c nper = (t-x(1))/p tp = t-float(nper)*p if (tp .lt. x(1)) tp = tp+p tt = tp c c check for illegal i c if (i .ge. n) i = n/2 c c check old interval and extremes c if (tt .lt. x(i)) then if (tt .le. x(2)) then i = 1 intrvp = 1 return else il = 2 ih = i end if else if (tt .le. x(i+1)) then intrvp = i return else if (tt .ge. x(n)) then i = n intrvp = n return else il = i+1 ih = n end if c c binary search loop c 1 i = (il+ih)/2 if (tt .lt. x(i)) then ih = i else if (tt .gt. x(i+1)) then il = i+1 else intrvp = i return end if go to 1 end ! subroutine snhcsh (sinhm,coshm,x,isw) !c ! integer isw ! real sinhm,coshm,x !c !c coded by alan kaylor cline !c from fitpack -- january 26, 1987 !c a curve and surface fitting package !c a product of pleasant valley software !c 8603 altus cove, austin, texas 78759, usa !c !c this subroutine returns approximations to !c sinhm(x) = sinh(x)/x-1 !c coshm(x) = cosh(x)-1 !c and !c coshmm(x) = (cosh(x)-1-x*x/2)/(x*x) !c with relative error less than 1.0e-6 !c !c on input-- !c !c x contains the value of the independent variable. !c !c isw indicates the function desired !c = -1 if only sinhm is desired, !c = 0 if both sinhm and coshm are desired, !c = 1 if only coshm is desired, !c = 2 if only coshmm is desired, !c = 3 if both sinhm and coshmm are desired. !c !c on output-- !c !c sinhm contains the value of sinhm(x) if isw .le. 0 or !c isw .eq. 3 (sinhm is unaltered if isw .eq.1 or isw .eq. !c 2). !c !c coshm contains the value of coshm(x) if isw .eq. 0 or !c isw .eq. 1 and contains the value of coshmm(x) if isw !c .ge. 2 (coshm is unaltered if isw .eq. -1). !c !c and !c !c x and isw are unaltered. !c !c----------------------------------------------------------- !c ! data sp13/.3029390e-5/, ! * sp12/.1975135e-3/, ! * sp11/.8334261e-2/, ! * sp10/.1666665e0/ ! data sp24/.3693467e-7/, ! * sp23/.2459974e-5/, ! * sp22/.2018107e-3/, ! * sp21/.8315072e-2/, ! * sp20/.1667035e0/ ! data sp33/.6666558e-5/, ! * sp32/.6646307e-3/, ! * sp31/.4001477e-1/, ! * sq32/.2037930e-3/, ! * sq31/-.6372739e-1/, ! * sq30/.6017497e1/ ! data sp43/.2311816e-4/, ! * sp42/.2729702e-3/, ! * sp41/.9868757e-1/, ! * sq42/.1776637e-3/, ! * sq41/-.7549779e-1/, ! * sq40/.9110034e1/ ! data cp4/.2982628e-6/, ! * cp3/.2472673e-4/, ! * cp2/.1388967e-2/, ! * cp1/.4166665e-1/, ! * cp0/.5000000e0/ !c ! ax = abs(x) ! if (isw .ge. 0) go to 5 !c !c sinhm approximation !c ! if (ax .gt. 4.45) go to 2 ! xs = ax*ax ! if (ax .gt. 2.3) go to 1 !c !c sinhm approximation on (0.,2.3) !c ! sinhm = xs*(((sp13*xs+sp12)*xs+sp11)*xs+sp10) ! return !c !c sinhm approximation on (2.3,4.45) !c ! 1 sinhm = xs*((((sp24*xs+sp23)*xs+sp22)*xs+sp21) ! . *xs+sp20) ! return ! 2 if (ax .gt. 7.65) go to 3 !c !c sinhm approximation on (4.45,7.65) !c ! xs = ax*ax ! sinhm = xs*(((sp33*xs+sp32)*xs+sp31)*xs+1.)/ ! . ((sq32*xs+sq31)*xs+sq30) ! return ! 3 if (ax .gt. 10.1) go to 4 !c !c sinhm approximation on (7.65,10.1) !c ! xs = ax*ax ! sinhm = xs*(((sp43*xs+sp42)*xs+sp41)*xs+1.)/ ! . ((sq42*xs+sq41)*xs+sq40) ! return !c !c sinhm approximation above 10.1 !c ! 4 sinhm = exp(ax)/(ax+ax)-1. ! return !c !c coshm and (possibly) sinhm approximation !c ! 5 if (isw .ge. 2) go to 7 ! if (ax .gt. 2.3) go to 6 ! xs = ax*ax ! coshm = xs*((((cp4*xs+cp3)*xs+cp2)*xs+cp1)*xs+cp0) ! if (isw .eq. 0) sinhm = xs*(((sp13*xs+sp12)*xs+sp11) ! . *xs+sp10) ! return ! 6 expx = exp(ax) ! coshm = (expx+1./expx)/2.-1. ! if (isw .eq. 0) sinhm = (expx-1./expx)/(ax+ax)-1. ! return !c !c coshmm and (possibly) sinhm approximation !c ! 7 xs = ax*ax ! if (ax .gt. 2.3) go to 8 ! coshm = xs*(((cp4*xs+cp3)*xs+cp2)*xs+cp1) ! if (isw .eq. 3) sinhm = xs*(((sp13*xs+sp12)*xs+sp11) ! . *xs+sp10) ! return ! 8 expx = exp(ax) ! coshm = ((expx+1./expx-xs)/2.-1.)/xs ! if (isw .eq. 3) sinhm = (expx-1./expx)/(ax+ax)-1. ! return ! end subroutine snhcsh (sinhm,coshm,x,isw) c integer isw real sinhm,coshm,x c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine returns approximations to c sinhm(x) = sinh(x)/x-1 c coshm(x) = cosh(x)-1 c and c coshmm(x) = (cosh(x)-1-x*x/2)/(x*x) c with relative error less than 4.0e-14. c c on input-- c c x contains the value of the independent variable. c c isw indicates the function desired c = -1 if only sinhm is desired, c = 0 if both sinhm and coshm are desired, c = 1 if only coshm is desired, c = 2 if only coshmm is desired, c = 3 if both sinhm and coshmm are desired. c c on output-- c c sinhm contains the value of sinhm(x) if isw .le. 0 or c isw .eq. 3 (sinhm is unaltered if isw .eq.1 or isw .eq. c 2). c c coshm contains the value of coshm(x) if isw .eq. 0 or c isw .eq. 1 and contains the value of coshmm(x) if isw c .ge. 2 (coshm is unaltered if isw .eq. -1). c c and c c x and isw are unaltered. c c----------------------------------------------------------- c data sp14/.227581660976348e-7/, * sp13/.612189863171694e-5/, * sp12/.715314759211209e-3/, * sp11/.398088289992973e-1/, * sq12/.206382701413725e-3/, * sq11/-.611470260009508e-1/, * sq10/.599999999999986e+1/ data sp25/.129094158037272e-9/, * sp24/.473731823101666e-7/, * sp23/.849213455598455e-5/, * sp22/.833264803327242e-3/, * sp21/.425024142813226e-1/, * sq22/.106008515744821e-3/, * sq21/-.449855169512505e-1/, * sq20/.600000000268619e+1/ data sp35/.155193945864942e-9/, * sp34/.511529451668737e-7/, * sp33/.884775635776784e-5/, * sp32/.850447617691392e-3/, * sp31/.428888148791777e-1/, * sq32/.933128831061610e-4/, * sq31/-.426677570538507e-1/, * sq30/.600000145086489e+1/ data sp45/.188070632058331e-9/, * sp44/.545792817714192e-7/, * sp43/.920119535795222e-5/, * sp42/.866559391672985e-3/, * sp41/.432535234960858e-1/, * sq42/.824891748820670e-4/, * sq41/-.404938841672262e-1/, * sq40/.600005006283834e+1/ data cp5/.552200614584744e-9/, * cp4/.181666923620944e-6/, * cp3/.270540125846525e-4/, * cp2/.206270719503934e-2/, * cp1/.744437205569040e-1/, * cq2/.514609638642689e-4/, * cq1/-.177792255528382e-1/, * cq0/.200000000000000e+1/ data zp4/.664418805876835e-8/, * zp3/.218274535686385e-5/, * zp2/.324851059327161e-3/, * zp1/.244515150174258e-1/, * zq2/.616165782306621e-3/, * zq1/-.213163639579425e0/, * zq0/.240000000000000e+2/ c ax = abs(x) if (isw .ge. 0) go to 5 c c sinhm approximation c if (ax .gt. 3.9) go to 2 xs = ax*ax if (ax .gt. 2.2) go to 1 c c sinhm approximation on (0.,2.2) c sinhm = xs*((((sp14*xs+sp13)*xs+sp12)*xs+sp11)*xs+1.)/ . ((sq12*xs+sq11)*xs+sq10) return c c sinhm approximation on (2.2,3.9) c 1 sinhm = xs*(((((sp25*xs+sp24)*xs+sp23)*xs+sp22)*xs+sp21) . *xs+1.)/((sq22*xs+sq21)*xs+sq20) return 2 if (ax .gt. 5.1) go to 3 c c sinhm approximation on (3.9,5.1) c xs = ax*ax sinhm = xs*(((((sp35*xs+sp34)*xs+sp33)*xs+sp32)*xs+sp31) . *xs+1.)/((sq32*xs+sq31)*xs+sq30) return 3 if (ax .gt. 6.1) go to 4 c c sinhm approximation on (5.1,6.1) c xs = ax*ax sinhm = xs*(((((sp45*xs+sp44)*xs+sp43)*xs+sp42)*xs+sp41) . *xs+1.)/((sq42*xs+sq41)*xs+sq40) return c c sinhm approximation above 6.1 c 4 expx = exp(ax) sinhm = (expx-1./expx)/(ax+ax)-1. return c c coshm and (possibly) sinhm approximation c 5 if (isw .ge. 2) go to 7 if (ax .gt. 2.2) go to 6 xs = ax*ax coshm = xs*(((((cp5*xs+cp4)*xs+cp3)*xs+cp2)*xs+cp1) . *xs+1.)/((cq2*xs+cq1)*xs+cq0) if (isw .eq. 0) sinhm = xs*((((sp14*xs+sp13)*xs+sp12) . *xs+sp11)*xs+1.)/((sq12*xs+sq11)*xs+sq10) return 6 expx = exp(ax) coshm = (expx+1./expx)/2.-1. if (isw .eq. 0) sinhm = (expx-1./expx)/(ax+ax)-1. return c c coshmm and (possibly) sinhm approximation c 7 xs = ax*ax if (ax .gt. 2.2) go to 8 coshm = xs*((((zp4*xs+zp3)*xs+zp2)*xs+zp1)*xs+1.)/ . ((zq2*xs+zq1)*xs+zq0) if (isw .eq. 3) sinhm = xs*((((sp14*xs+sp13)*xs+sp12) . *xs+sp11)*xs+1.)/((sq12*xs+sq11)*xs+sq10) return 8 expx = exp(ax) coshm = ((expx+1./expx-xs)/2.-1.)/xs if (isw .eq. 3) sinhm = (expx-1./expx)/(ax+ax)-1. return end subroutine terms (diag,sdiag,sigma,del) c real diag,sdiag,sigma,del c c coded by alan kaylor cline c from fitpack -- january 26, 1987 c a curve and surface fitting package c a product of pleasant valley software c 8603 altus cove, austin, texas 78759, usa c c this subroutine computes the diagonal and superdiagonal c terms of the tridiagonal linear system associated with c spline under tension interpolation. c c on input-- c c sigma contains the tension factor. c c and c c del contains the step size. c c on output-- c c sigma*del*cosh(sigma*del) - sinh(sigma*del) c diag = del*--------------------------------------------. c (sigma*del)**2 * sinh(sigma*del) c c sinh(sigma*del) - sigma*del c sdiag = del*----------------------------------. c (sigma*del)**2 * sinh(sigma*del) c c and c c sigma and del are unaltered. c c this subroutine references package module snhcsh. c c----------------------------------------------------------- c if (sigma .ne. 0.) go to 1 diag = del/3. sdiag = del/6. return 1 sigdel = sigma*del call snhcsh (sinhm,coshm,sigdel,0) denom = sigma*sigdel*(1.+sinhm) diag = (coshm-sinhm)/denom sdiag = sinhm/denom return end