Two dimensional extrapolation

Does anyone know how to do two-dimensional extrapolation for out of range values?

Z=interp2(X,Y,Z,XI,YI).

In Matlab, you specify "extrapval" for out of range values. If I don't want to specify a value but actually want to extrapolate, any easy way of doing it in Matlab?

Thanks!

Answer 1

[John D'Errico]

I posted the function interpne on the FEX a few years ago. It does what you want, as long as you want linear extrapolation.

http://www.mathworks.com/matlabcentral/fileexchange/10522

Note: extrapolation is a dangerous business.

Answer 2

[Dan]

You can calculate the derivatives than use linear extrapolation using these derivatives. Another way is to re-implement interp2 to incorporate that feature.