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Re: naive question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92842] Re: naive question
  • From: Albert Retey <awnl at gmx-topmail.de>
  • Date: Tue, 14 Oct 2008 05:01:21 -0400 (EDT)
  • References: <gcv7ku$e63$1@smc.vnet.net>

Francisco Gutierrez wrote:
> Dear Friends:
> I am using Fit within a function, and I want it to produce only a list of
>  coefficients, without the variables.
> For example, if I plug into fit the following: Fit[{{1,2,3},{4,5,6},{7,8,9}},{1,x1,x2},{x1,x2}],
> Mathematica produces:
> 1.55556+0.555556 x1+0.444444 x2
>  
> I want to get only the following list:
> {1.55556,0.555556,0.444444}
>  
> It seem awfully simple, but I haven't managed.
> How can I do it?
> Thanks
> Francisco

Look at the functions CoefficientList and Coefficient. For your case you
need some extra effort since CoefficientList arranges the coefficients
in an other way:

CoefficientList[
 Fit[{{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}, {1, x1, x2}, {x1, x2}],
 {x1, x2}
 ]

hth,

albert


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