Hello, I would like some help to discover a function ( f(x,y) ) that describes a surface that was determined through a curve fitting using the Matlab tool "Curve fitting". Afterwards I selected "Interpolant" >> "Biharmonic".

I have three columns with numerical data. From these data, determined numerically, I would like to find an equation (f (x,y) ), which will give me the value of the z axis, if I inform the value of the x and y axis. So I searched for the feature in Matlab through curve fitting to find the function. I noticed that a fifth degree polynomial fit for x and y doesn't look good. So I had to turn to Interpolant. The software plotted a perfect figure, which properly fit the distribution of points. But I can't find the surface equation generated by Matlab.

If anyone can help me I would be very grateful