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Basically, I have a symsum which I intend on feeding into a fittype() function.

The fittype is of the form (V0/2) + (V1/2)*cos(1*x) + (V2/2)*cos(2*x) +... (Vn/2)*cos(n*x) where each Vn is an independent variable in a non-linear least squares.

Those Vn variables are going into a matrix so the values need to be extractable, right now I'm using coeffvalues(fitresult) or manually getting them out with fitresult.V0, V1 etc (that could be a question on its own).

I have the sum of cos funcs

syms x n

Func = symsum((1/2)*cos(n*x),n,[1 5])

but I can't figure out how to (1) create an array of variables V0:Vn and outputting them as variables and (2) how to combine those with a symsum output into the fittype given above.

Chaitanya Mallela
on 4 Feb 2021

Edited: Chaitanya Mallela
on 4 Feb 2021

fittype function accepts character array as input argument but the symsum function gives symbolic variable. To apply fittype to this function you need to split the symsum expression into terms and convert them to character array and generate independent variable Vn as coefficients to fittype function.

syms x n

Func = cell2sym(children(symsum((1/2)*cos(n*x),n,[1 5])));

g = fittype(arrayfun(@char,Func,'UniformOutput',false),'coefficients',arrayfun(@char,sym('V',[1,5]),'UniformOutput',false))

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