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*Subject*: Re: Help: Weighted quadratic fitting under IDL?*From*: Martin Schultz <martin.schultz(at)dkrz.de>*Date*: Wed, 15 Mar 2000 09:45:57 -0100*Newsgroups*: comp.lang.idl-pvwave*Organization*: MPI fuer Meteorologie*References*: <8amb67$otd$1@peabody.colorado.edu>*Xref*: news.doit.wisc.edu comp.lang.idl-pvwave:18924

There is only one answer: MPFIT Grab it from http://cow.physics.wisc.edu/~craigm/idl/ Cheers, Martin "Brad K. Gibson" wrote: > > This may be a highly trivial question, but it's one I'm having problems > dealing with under IDL. Perhaps I"m simply missing something obvious .. > regardless, I'd be indebted if someone could help me out. Heck, I'll even > throw in a nice acknowledgement in my next paper, if someone could point me to > a simple solution, or provide the requisite few lines of code! > > Anyways ... here it is ... the equation of interest is of the form: > > Vmax - 5*log(v) = a[m15-1.1] + b[m15-1.1]^2 + c > > I have a data file with Vmax, v, and m15 for a set of objects (about 40 of > them), with uncertainties on each value. > Having read those entries in, what I want to do is fit the above > functional form, deriving a, b, and c, as well as their associated > uncertainties (i.e. a +/- sig(a), b +/- sig(b), and c+/-sig(c)), and the final > dispersion (and maybe reduced chi-squared) of the best fit quadratic. > > Now .. I can see various routines which get me part-way there, but they either > only provide a,b, and c without uncertainties, or only provide the > uncertainties for a linear fit (e.g. fitexy). Basically what I'd like is a > quadratic version of fitexy (i.e., sigmas on all returned coefficients+ > dispersion of fit+reduced chi-square). > > Obviously there is a nice way to do this without doing Monte Carlo > simulations, but anyone who could save me a few > hours of hacking code would become my instant hero(ine). Anyone? > > Cheers, > Brad > > -- > Brad K. Gibson INTERNET: bgibson@casa.colorado.edu > CASA, University of Colorado PHONE: +1-303-492-6058 > Campus Box 389 FAX: +1-303-492-7178 > Boulder, CO, USA 80309-0389 http://casa.colorado.edu/~bgibson/ -- [[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[ [[ Dr. Martin Schultz Max-Planck-Institut fuer Meteorologie [[ [[ Bundesstr. 55, 20146 Hamburg [[ [[ phone: +49 40 41173-308 [[ [[ fax: +49 40 41173-298 [[ [[ martin.schultz@dkrz.de [[ [[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[

**References**:**Help: Weighted quadratic fitting under IDL?***From:*Brad K. Gibson

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