Getting the value of a graph at a certain point

I had (x,y,z) data and got a surface from these values by curve fitting. Now I want to get the z-value at a point (x,y), which was not in the data set, with which I created the graph. Is that possible and how can I do this?

Answer 1

[Julien]

you have to make a 2D interpolation

 interp2(X,Y,Z,xi,yi)

with X,Y,Z : values from your datas (xi,yi) the coordinates of the point you want to find

look inside documentation for additional information

Answer 2

[Matt J]

If you performed a curve fit, then it should have given you a continuous-space formula z=f(x,y) for the surface. Just evaluate the formula at the point(s) you're interested in. Wasn't that the whole point of doing the curve fit in the first place?