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Topic: Difference of cost functions in optimization?
Replies: 2   Last Post: Feb 22, 2013 6:32 AM

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Alan Weiss

Posts: 1,255
Registered: 11/27/08
Re: Difference of cost functions in optimization?
Posted: Feb 21, 2013 1:38 PM
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On 2/21/2013 6:16 AM, Pascal Schulthess wrote:
> Hi everyone,
>
> I'm working quite a long time with lsqnonlin and comparable functions
> but now I'm wondering if there's a difference between the following
> two expressions of the cost function:
>
> First:
> f = [0,1];
> function error = objFcn(p, x, y)
> fit = zeros(size(ydata));
> for i = 1:size(ydata, 1)
> fit(i,:)= p(1)*x + f(i)*p(2);
> end
> error = fit-y;
> end
>
> And, secondly:
> function error = objFcn(p, x, y)
> fit = zeros(size(ydata));
> fit(1,:)= p(1)*x;
> fit(2,:)= p(1)*x + p(2);
> error = fit-y;
> end
>
> I would really appreciate any help and possible explanations.
>
> Thanks a lot,
>
> Pascal


Well, I'm not sure what is the error or warning you are seeing, or what
is the problem you are experiencing.

If I have to guess, it seems to me that the "fit" matrix has a different
size in the second formulation than in the first. But I really don't
know, because you haven't told us the size of your matrices.

Alan Weiss
MATLAB mathematical toolbox documentation



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