Surface fit x y vector data with length(x)*length(y) size Z matrix

Hello,

I am reposting a question to clear some things up from my previous post. Let me introduce the problem again:

I have an x vector and y vector of data, for which I have the results for each row index combination of x and y stored in matrix Z. x and y are the same size and Z is a matrix where the row and column length is the same as the row size of x and y.

I would like to obtain a fit of the following form: (a+b*x+c*x^2)+(d+e*x+f*x^2)*sin(y)+(g+h*x+ii*x^2)*cos(y), where a,b,c,d,e,f,g,h,ii (yes not i;so that imaginary is not overwritten) are the constants. For this, I have the following code:

myfittype = fittype('(a+b*x+c*x^2)+(d+e*x+f*x^2)*sin(y)+(g+h*x+ii*x^2)*cos(y)',...
    'dependent',{'Z'},'independent',{'x','y'},...
    'coefficients',{'a','b','c','d','e','f','g','h','ii'});

fitCL=fit([x y],Z,myfittype);

This however results in the following error:

Operator '<' is not supported for operands of type 'fittype'.

Error in fit (line 7)
if dim_x < m

[Cris LaPierre]

You stopped responding on your previous question.

[Alessandro Maria Laspina]

There was confusion on which method I was trying to use. I posted a new question because I am strictly trying to find a fit to the equation and interp is not what I need.

[Cris LaPierre]

Save your variables x,y and Z to a mat file and attach it to your post using the paperclip icon.

When I run your code for myfittype, I do not get the error you report. Please share the entire error message (all the red text).

[darova]

Why do you need such complicated formula? Can you attach/show the data?