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Help with a fit

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aurc89
aurc89 2014년 3월 21일
댓글: aurc89 2014년 3월 21일
Hello! I have a set of data (x,y) which describes a function y=f(x). I would like to fit this function with a biexponential function made like this : f(x) = a*exp(-x/b)+c*exp(-x/d)+e and retrieve the values of a,b,c,d,e. Can you help me to do this? Thank you!

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Mischa Kim
Mischa Kim 2014년 3월 21일
편집: Mischa Kim 2014년 3월 21일
Aurc89, does this help?
a = 1; b = 1; c = 1; d = 1; e = 1;
x = (0:0.1:2)';
y = a*exp(-x/b)+c*exp(-x/d)+e + 0.1*rand(length(x),1);
f = fit(x,y,'exp2');
plot(f,x,y)
The fitting coefficients are accessed, e.g., via
f.a
  댓글 수: 8
Mischa Kim
Mischa Kim 2014년 3월 21일
편집: Mischa Kim 2014년 3월 21일
Aurc89: You're welcome.
John: I was not trying to generate random noise, thanks for the polite pointer, though.
aurc89
aurc89 2014년 3월 21일
Sorry, the last question: this kind of command gives me the fit with the function f(x) = a*exp(b*x) + c*exp(d*x). Instead, I woud like to have a fit with this kind of function: f(x) = a*exp(b*x) + c*exp(d*x) + g. I need the constant term g also, because the time constants of the biexponential changes with g (because I am differently close to zero axis by changing 'g', so b and d are different). Is there an authomatic way to do this? Thank you very much in advance

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