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

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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
  4 Comments
Cris LaPierre
Cris LaPierre on 20 Mar 2021
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
darova on 20 Mar 2021
Why do you need such complicated formula? Can you attach/show the data?

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