MATLAB find coefficients for a specific equation?

I was given the equation:
Ft=A0+(A1*t)+(A2*cos(t*w0))+(B1*sin(t*w0));
w0=(2*pi/365);
I am given a vector of 900 points for t,Ft coordinates and need to find the coefficients to give me the best fit for the given equation.
How would I do that?

6 comentarios

Image Analyst
Image Analyst el 6 de Mzo. de 2018
Please attach your t and Ft data in a .mat file. You might try using fitnlm() in the stats toolbox.
John D'Errico
John D'Errico el 6 de Mzo. de 2018
What do you have?
Stats toolbox? REGRESS will be sufficient, since w0 is known.
Curve fitting toolbox? FIT will suffice.
No toolbox? Backslash, or lsqr, Lots of options.
So depending on what you have there are lots of solutions. But before we can offer the best advise, we need to know what you have.
Michelle Babak
Michelle Babak el 6 de Mzo. de 2018
Editada: Walter Roberson el 7 de Mzo. de 2018
I downloaded curve fitting toolbox and tried to use it:
t=Time1-22232;
w0=(2*pi/365);
X=fittype('A0+(A1*Time)+(A2*cos(Time*w0))+(B1*sin(Time*w0))','coeff',{'A0','A1','B1','B2'});
fit(t,Thick,X)
Time, Thick are the coordinates I am given
It still didnt work.
X = fittype(@(A0,A1,A2,B1,Time) A0+(A1*Time)+(A2*cos(Time*w0))+(B1*sin(Time*w0)), 'Independent', 'Time');
And then how do you use the fit() function with that?
fit_results = fit(t(:), Thick(:), X)
You might want to add a 'Startpoint' option with an initial guess

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el 6 de Mzo. de 2018

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el 7 de Mzo. de 2018

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