I have a data set consisting of points (x,y,z) where x and y are independent variables in an expt and z is the dependent variable. I want to find the correlation between this data set and two models (equations) each of which predicts a particular surface in the 3D space. Is there an [easy] way of doing this?
IÂ¹ve tried using various software packages but they have the annoying habit of first varying the equation parameters so as to provide a least squares fit. I just want to know the direct correlation between the equations as given and the data set.
Also is it valid to compare the two correlations when one equation is linear (x+y)/2 and the other is non-linear Sqrt[xy]?