BUG DESCRIPTION:
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In eval_cshep2d documentation one can read [zp [,dzpdx, dzpdy [,d2zpdxx,d2zpdxy,d2zpdyy]]] = eval_cshep2d(xp, yp, tl_coef) after several test it seams that d2zpdxy and d2zpdyy are to be switched.
Correct function prototype shall be : [zp [,dzpdx, dzpdy [,d2zpdxx,d2zpdyy,d2zpdxy]]] = eval_cshep2d(xp, yp, tl_coef)
ERROR LOG:
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HOW TO REPRODUCE THE BUG:
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Compare the second derivates between cshep2d and splin2d or with a known function
grid=linspace(0,2*%pi,100)
[X,Y]=ndgrid(grid,grid)
Z=cos(X).*cos(Y)
x=X(:)
y=Y(:)
z=Z(:)
C=splin2d(grid,grid,Z)
[zpS, dzpdxS dzpdyS, d2zpdxxS, d2zpdxyS, d2zpdyyS]=interp2d(X, Y, grid, grid, C)
tl_coef=cshep2d(cat(2,x,y,z))
[zp, dzpdx, dzpdy, d2zpdxx, d2zpdyy, d2zpdxy]=eval_cshep2d(X, Y, tl_coef)
mesh(X,Y,d2zpdxy-sin(X).*sin(Y))
OTHER INFORMATION:
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