Please note that the recommended version of Scilab is 2025.0.0. This page might be outdated.
See the recommended documentation of this function
cshep2d
bidimensional cubic shepard (scattered) interpolation
Calling Sequence
tl_coef = cshep2d(xyz)
Arguments
- xyz
a n x 3 matrix of the (no gridded) interpolation points (the i th row given the (x,y) coordinates then the altitude z of the i th interpolation point)
- tl_coef
a tlist scilab structure (of type cshep2d)
Description
This function is useful to define a 2d interpolation function when
the interpolation points are not on a grid (you may use it in this case
but splin2d is better for that purpose).
The interpolant is a cubic shepard one and is a C2 (twice continuously
differentiable) bivariate function s(x,y) such that :
s(xi,yi)=zi for all i=1,..,n
((xi,yi,zi) being the i th row of
xyz
).
The evaluation of s at some points must be done by the eval_cshep2d function.
Remark
The function works if n>= 10, if the nodes are not all colinears (i.e. the (x,y) coordinates of the interpolation points are not on the same straight line), and if there is no duplicate nodes (i.e. 2 or more interpolation points with the same (x,y) coordinates). An error is issued if these conditions are not respected.
Examples
// interpolation of cos(x)cos(y) with randomly chosen interpolation points n = 150; // nb of interpolation points xy = grand(n,2,"unf",0,2*%pi); z = cos(xy(:,1)).*cos(xy(:,2)); xyz = [xy z]; tl_coef = cshep2d(xyz); // evaluation on a grid m = 30; xx = linspace(0,2*%pi,m); [X,Y] = ndgrid(xx,xx); Z = eval_cshep2d(X,Y, tl_coef); clf() plot3d(xx,xx,Z,flag=[2 6 4]) param3d1(xy(:,1),xy(:,2),list(z,-9), flag=[0 0]) xtitle("Cubic Shepard Interpolation of cos(x)cos(y) with randomly chosen interpolation points") legends("interpolation points",-9,1) show_window()
See Also
- splin2d — bicubic spline gridded 2d interpolation
- eval_cshep2d — bidimensional cubic shepard interpolation evaluation
History
Version | Description |
5.4.0 | previously, imaginary part of input arguments were implicitly ignored. |
Report an issue | ||
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