Interpolation with quadratic data

I need to perform a 2D interpolation, but have quadratic data. Are there any built-in MATLAB functions that can handle interpolation on a quadratic array? I tried to sort the data (i.e., sort(x)) to arrange it in ascending order and passing it through the interp2 function, but it did not produce what was expected. Hence, I believe I need to keep the data in the arrangement it's in and determine a way to interpolate it.

Any assistance is appreciated

[Jon]

You should look at http://www.mathworks.com/help/matlab/ref/mkpp.html