| Re: sigma in curvefit function! [message #39347] |
Thu, 13 May 2004 11:20  |
marcuirl
Messages: 14
Registered: December 2003
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Junior Member |
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<Raquel.Niclos@uv.es> writes:
> Hello,
>
> I was trying to use IDL curvefit function in order to obtain the
> fitting parameters for a non-linear equation. This equation needs a
> fixed parameter to be read from an external file, so I wrote a
> program that read x,y and this parameter from a file, then it call
> the curvefit function (I modified it in order to read this extra
> parameter) with the corresponding function_name (where is my
> equation, which uses this fixed parameter).
> The problem is that I�m using the no-weighting form (because I�m
> fitting one model results to another theoretical equation) and I
> obtained nonsense values for the standard deviations on the fitted
> coefficients (sigma). I read something about this, and I tried with
> the mpcurvefit function too, but I didn't know how to read the
> external fixed parameter from the mpcurvefit function (I didn�t know
> modify it in this case)
>
> Has anybody a solution? Has anybody an alternative program?
To quote David Fanning 03-May 14:26 in this very group, right here yes
(i.e. http://tinyurl.com/23ro5)
<quote David Fanning>
Yes, abandon CURVEFIT and get on over to Craig's site and pick
up MPFIT, the fitting software the professionals use. :-)
http://cow.physics.wisc.edu/~craigm/idl/fitting.html
</quote David Fanning>
TWH, marcu
--
Unless otherwise noted, the statements herein reflect my
personal opinions and not those of any organisation with
which I may be affiliated.
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