Polynomial fitting with dependent variables
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How can I obtain a polynomial fitting in Matlab having coefficients depending on another variable ? e.g I have variables X1 and Y and I want to find the line (polynomial of degree 1) that fits Y=f(X1)=p0+p1*X1. That would result in the two polynomial coefficients p0,p1 with the function polyfit. Now, I would like to obtain a fitting for which the coefficients p0,p1 depend (linearly) on another variable X2 so p0=f1(X2)=a*X2+b, p1=f2(X2)=c*X2+d.
That would finally result in Y=f1(X2)+f2(X2)*X1.
How to do that ?
Thanks in advance.
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Accepted Answer
Torsten
on 13 Oct 2016
In this case, your model is of the form
Y=c*X1*X2+d*X1+a*X2+b
and you have to estimate the coefficients a,b,c and d.
Since this model is also linear in the coefficients, you can use the same method as for the model
Y=p0+p1*X1
Best wishes
Torsten.
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