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Re: request for help with fmins or fminbnd

From: Søren Hauberg
Subject: Re: request for help with fmins or fminbnd
Date: Fri, 31 Aug 2007 17:02:02 +0200
User-agent: Thunderbird (X11/20070604)

I'm not quite sure what your question is, but I get the feeling that your problem is with passing parameters to the function you wish to minimize. I rarely use 'fmins', so I don't know if it has any quirks you need to work around. However, if your just having problems with passing arguments, I guess you could do something like this:

  f = @(x) Likelihood_pois1(x, pir, boundslowmax, boundsupmax);
  fmins(f, initparammax)


Tracy Feldman skrev:
To whom it may concern:
I am trying to convert a program that had worked well in Matlab, so that I can use an equivalent program in Octave (I no longer have access to Matlab). The program calculates the maximum likelihood estimate and the best-fit parameters for a function (finding poisson confidence limits, in this case, or in other cases, fitting a logistic function with binomial error). I have run into difficulties with the fmins function (which I have used in Octave to replace “fminsearch” in Matlab). I am trying to call my likelihood function as follows: [maxparam, maxlike] = fmins(@Likelihood_pois1, initparammax, [], [], pir, boundslowmax, boundsupmax); where
maxparam is a vector of two values of the maximized function
Likelihood_pois1 is the likelihood function (which I could send if it would help)
initparammax is a vector of two initial parameter values
the two [] sets are for Options and GRAD, respectively
pir is a response variable (the data)
boundslowmax is a vector of two lower bounds of the parameter values
boundsupmax is a vector of two upper bound of the parameter values
It is received by the Likelihood function as follows: function neglogL = Likelihood_pois1(pp, initparammax, pir, boundslowmax, boundsupmax); I am not sure what would be the correct syntax, but whatever order I choose for the variables in parentheses (or if I get rid of one or both of the empty brackets) I get an error message saying invalid vector index = 4 (or some other #), and that fmins cannot perform any of several binary operations. I have also tried converting to syntax for fminbnd, hoping it would be better, but this will not work for me either. Is this more than a simple syntax issue? I would appreciate any suggestions you might have (or if you would like more code from me and/or the program files, I can send more--or original files that worked in Matlab). I really appreciate your time and help. I am not currently subscribed to the list, so if you can, please respond to me directly at address@hidden <mailto:address@hidden>.
Tracy S. Feldman Postdoctoral Associate
The Samuel Roberts Noble Foundation
Ardmore, OK 73401
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