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MathGroup Archive 1997

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Re: Questions on fitting and plotting data

  • To: mathgroup at smc.vnet.net
  • Subject: [mg7993] Re: Questions on fitting and plotting data
  • From: Paul Abbott <paul at physics.uwa.edu.au>
  • Date: Wed, 30 Jul 1997 23:57:45 -0400
  • Organization: University of Western Australia
  • Sender: owner-wri-mathgroup at wolfram.com

Daniel Goscha wrote:

> In[38]:=
> t2 = {{1, 1.5, .5}, {2.3, 2.8, .5}, {3, 3.7, .5}, {4.2, 4.6, .5},
>   {5.1, 5, .5}, {6.4, 6.4, .5}, {7.2, 7.7, .5}, {8, 8.9, .5}}
> Out[38]=
> {{1,1.5,0.5},{2.3,2.8,0.5},{3,3.7,0.5},{4.2,4.6,0.5},{5.1,5,0.5},{6.4,6.4,
> 
>     0.5},{7.2,7.7,0.5},{8,8.9,0.5}}
> 
> In[39]:=
> plot1 = ErrorListPlot[t2]
> 
> **now, here is where I start getting the problems - this is obviously
> NOT the correct least-square fit solution to the data I have
> specified.**

You need to drop the error (i.e. last) component from t2 before fitting:

 In[41]:= Drop[#1, -1]& /@ t2

 Out[41]= {{1, 1.5}, {2.3, 2.8}, {3, 3.7}, {4.2, 4.6}, {5.1, 5}, 
  {6.4, 6.4}, {7.2, 7.7}, {8, 8.9}}

 In[42]:= Fit[%, {1, x}, x]
 Out[42]= 0.997895 x + 0.434787

Cheers,
	Paul 

____________________________________________________________________ 
Paul Abbott                                   Phone: +61-8-9380-2734
Department of Physics                           Fax: +61-8-9380-1014
The University of Western Australia           
Nedlands WA  6907                     mailto:paul at physics.uwa.edu.au 
AUSTRALIA                              http://www.pd.uwa.edu.au/Paul

            God IS a weakly left-handed dice player
____________________________________________________________________


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