
Re: Difference of cost functions in optimization?
Posted:
Feb 22, 2013 6:32 AM


Alan_Weiss <aweiss@mathworks.com> wrote in message <kg5piv$7ss$1@newscl01ah.mathworks.com>... > 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 = fity; > > 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 = fity; > > 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
Hi, there's no error message. It's more a general question. Ok, so, in the first case, p(2) is basically present in both equations (fit(1,:) and fit(2,:)) except that it is multiplied by a factor (0). My question now is if p(2) is also considered by the fitting routine in fit(1,:) or (as it should be) only in fit(2,:)? I hope I made myself clear. Thanks, Pascal

