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MathGroup Archive 1998

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Re: Duplicate Elements in List cause Errors with Interpolation


  • To: mathgroup@smc.vnet.net
  • Subject: [mg10707] Re: Duplicate Elements in List cause Errors with Interpolation
  • From: Paul Abbott <paul@physics.uwa.edu.au>
  • Date: Fri, 30 Jan 1998 04:24:42 -0500
  • Organization: University of Western Australia
  • References: <6ahp25$pkv@smc.vnet.net>

Todd Rose wrote:

> This doesn't seem to work for me.  I can't figure out how to remove the
> duplicate in the first element of the data pairs (0.4375).  Union only
> seems to work if they are alike in both the abscissa and the ordinate.
> Perhaps I can use a test with the Union command, but I have not been
> able to figure out the format for the "spec".

In[2]:= mydata = Union[mydata, SameTest -> (First[#1] == First[#2] & )];


removes duplicate first elements.

In[3]:= lp = ListPlot[mydata]; 
In[4]:= myfunction = Interpolation[%, InterpolationOrder -> 1];

However, for this dataset, why use Interpolation anyway?  I think a Fit
is a much better idea:

In[5]:= fit[x_] = Fit[mydata, {1, Sqrt[x], x}, x] Out[5]= -17.9046 x +
116.859 Sqrt[x] - 13.4646

In[6]:=Plot[fit[x], {x, 0, 5.3}];  

In[7]:= Show[%, lp]; 

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@physics.uwa.edu.au  AUSTRALIA                            
http://www.pd.uwa.edu.au/~paul

            God IS a weakly left-handed dice player
____________________________________________________________________



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