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fit gives different results for identical functions with different var names

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Subject	fit gives different results for identical functions with different var names
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I am using gnuplot for windows, trying to fit gaussian data. I am doing this from a program that has to run many fits on different sets of data, so I would like to use different variable names. Unfortunately, it seems that unless I use single-character names, I get completely unreasonable results. The results are identical for the same data for every function with variable names more than one charcter long, but always reasonable for functions with variables only one variable long.

For example: 
fa(xa) = aa*exp(-(xa-ma)**2/(2*sa**2)) 
gives results identical to f2(x2) = a2*exp(-(x2-m2)**2/(2*s2**2)), but different from f(x) = a*exp(-(x-m)**2/(2*s**2))

I cannot find any restriction on length of variable names in the documentation.
Any ideas?

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fit gives different results for identical functions with different var names marcus.hanson@gmail.com - 2012-12-20 13:01 -0800
  Re: fit gives different results for identical functions with different var names Brendan Halpin <brendan.halpin@ul.ie> - 2012-12-21 00:55 +0000
  Re: fit gives different results for identical functions with different var names Karl <mail.kfr@gmx.net> - 2012-12-21 12:42 +0100
    Re: fit gives different results for identical functions with different var names Marcus Hanson <marcus.hanson@gmail.com> - 2012-12-21 07:32 -0800
      Re: fit gives different results for identical functions with   different var names Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2012-12-21 19:21 +0100
        Re: fit gives different results for identical functions with   different var names Marcus Hanson <marcus.hanson@gmail.com> - 2012-12-21 11:54 -0800
          Re: fit gives different results for identical functions with     different var names Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2012-12-22 01:31 +0100

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