Description:
Subroutine pda_bispev evaluates on a grid (x(i),y(j)),i=1,...,mx;
j=1,...,my a bivariate spline s(x,y) of degrees kx and ky, given in
the b-spline representation.
Calling Sequence:
call pda_bispev( tx, nx, ty, ny, c, kx, ky, x, mx, y, my, z, wrk, lwrk,
iwrk, kwrk, ier )
Input Parameters:
tx : Real array, length nx, which contains the position of the
knots in the x-direction.
nx : Integer, giving the total number of knots in the x-direction
ty : Real array, length ny, which contains the position of the
knots in the y-direction.
ny : Integer, giving the total number of knots in the y-direction
c : Real array, length (nx-kx-1)*(ny-ky-1), which contains the
b-spline coefficients.
kx,ky : Integer values, giving the degrees of the spline.
x : Real array of dimension (mx). Before entry x(i) must be set to
the x co-ordinate of the i-th grid point along the x-axis.
tx(kx+1)<=x(i-1)<=x(i)<=tx(nx-kx), i=2,...,mx.
mx : Integer. On entry mx must specify the number of grid points along
the x-axis. Mx >=1.
y : Real array of dimension (my). Before entry y(j) must be set to
the y co-ordinate of the j-th grid point along the y-axis.
ty(ky+1)<=y(j-1)<=y(j)<=ty(ny-ky), j=2,...,my.
my : Integer. On entry my must specify the number of grid points along
the y-axis. My >=1.
wrk : Real array of dimension lwrk. Used as workspace.
lwrk : Integer, specifying the dimension of wrk.
lwrk >= mx*(kx+1)+my*(ky+1)
iwrk : Integer array of dimension kwrk. Used as workspace.
kwrk : Integer, specifying the dimension of iwrk. Kwrk >= mx+my.
Output Parameters:
z : Real array of dimension (mx*my). On successful exit z(my*(i-1)+j)
contains the value of s(x,y) at the point
(x(i),y(j)),i=1,...,mx;j=1,...,my.
ier : Integer error flag:
0 : Normal return.
10 : Invalid input data (see restrictions).
Restrictions:
mx >=1, my >=1, lwrk>=mx*(kx+1)+my*(ky+1), kwrk>=mx+my
tx(kx+1) <= x(i-1) <= x(i) <= tx(nx-kx), i=2,...,mx
ty(ky+1) <= y(j-1) <= y(j) <= ty(ny-ky), j=2,...,my
Other Subroutines Required:
pda_fpbisp, pda_fpbspl
References :
de Boor C : "On calculating with b-splines", j. Approximation theory
6 (1972) 50-62.
Cox M.G. : "The numerical evaluation of b-splines", j. inst. maths
applics 10 (1972) 134-149.
Dierckx P.: "Curve and surface fitting with splines", monographs on
numerical analysis, Oxford University Press, 1993.
Author :
P. Dierckx
Dept. Computer Science, k.u.leuven
celestijnenlaan 200a, b-3001 heverlee, Belgium.
e-mail : Paul.Dierckx@cs.kuleuven.ac.be
Latest Update : march 1987