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Curve fitting using custom model

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Kyle Wang
Kyle Wang 2015-7-28
评论： Elias 2015-7-28
Given set of x and y, how can I solve the parameter a, b and c in the model
y = a * x^b + c
to best fit the given data?
As I will further implement the algorithm in C++, I would prefer not using built-in Matlab functions to solve parameters.
Could anyone please suggest an algorithm? Many thanks, Kyle.
  2 个评论
Walter Roberson
Walter Roberson 2015-7-28
Are a and x certain to be non-negative ?
Kyle Wang
Kyle Wang 2015-7-28
the given data set x_given and y_given are vectors of positive double numbers. a, b and c could be negative or positive.

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Walter Roberson
Walter Roberson 2015-7-28
G = @(abc) sum((abc(1)*x0.^abc(2)+abc(3)-y0).^2);
ABC = fminsearch(G, [rand,rand,rand], 'MaxIters', 10000)
the result will not necessarily be exactly correct, and you can pass ABC back in instead of [rand,rand,rand], but I did find that with my test sometimes it cycled near the answer.
fminsearch is a gradient descent method.

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Torsten
Torsten 2015-7-28

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