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*Subject*: Re: gaussfit question*From*: "mirko" <mirko.loehmann(at)student.uni-magdeburg.de>*Date*: Mon, 1 Nov 1999 20:53:30 +0100*Newsgroups*: comp.lang.idl-pvwave*Organization*: Otto-von-Guericke-Universitaet Magdeburg*References*: <3819a9eb@loriot.cs.uni-magdeburg.de> <MPG.128368d1127e0f04989923@news.frii.com>*Xref*: news.doit.wisc.edu comp.lang.idl-pvwave:17028

David Fanning wrote: >Why don't you continue on a bit and see if you >get the result you expect. Yes I did. I have the feeling it was more or less my fault. >From my data it is clear that the centre of the gaussian should be somewhere in the middle between 0 an 36 which is not the case here for a[1]. Doing an 'oplot, x,yfit' gives a nice fit but not the right solution to the problem (fitting a gaussian). IDL> y=[52.0,52.7,56.0,60.9,65.40,71.40, 75.20, 80.80,86.1,89.8,88.3,94.8,94.9,100.5,100.1,103.9,105.3,106.2,107.3, 108.2,106.1,105.7,107.8,102.2, 101.3,97.2,92.1,87.4,87.0,82.5,77.4,69.9,67.7, 62.1, 58.9, 53.4,53.8] IDL> x=findgen(37) IDL> yfit=gaussfit(x,y,a) % Program caused arithmetic error: Floating underflow IDL> print,a -92.8950 38.7370 9.73786 48.4928 4.97301 -0.0657729 Using the estimates keyword and removing the linear and quadratic term results in the proper solution. IDL> yfit=gaussfit(x,y,a, nterms=4,estimates=[90.0,20.0,10.0,10.0]) IDL> print,a 96.7115 18.2423 13.4573 10.8630 without ESTIMATES the starting values for the fit seem not close enough IDL> yfit=gaussfit(x,y,a, nterms=4) % Program caused arithmetic error: Floating underflow IDL> print,a -35.3286 35.3296 3.44060 89.3350 Therefore I think I have to supply estimates to GAUSS2DFIT() in the case I like to fit an surface because this routine uses GAUSSFIT(). Thanks for the help Mirko

**References**:**gaussfit question***From:*mirko

**Re: gaussfit question***From:*David Fanning

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