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MathGroup Archive 2007

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Re: Regression

  • To: mathgroup at smc.vnet.net
  • Subject: [mg73857] Re: [mg73835] Regression
  • From: Sseziwa Mukasa <mukasa at jeol.com>
  • Date: Fri, 2 Mar 2007 06:29:23 -0500 (EST)
  • References: <200703011124.GAA28430@smc.vnet.net>

On Mar 1, 2007, at 6:24 AM, Anurag wrote:

> Hi,
> I am doing regression using mathematica. The code is
> simple. I define a polynomial. Read the data points
> from a file. I make sure that there are 27 data points
> in the file and all the 27 data points are unique.
>
> polynomial = Flatten[Table[x^i y^j z^k, {i, 0, 2}, {j,
> 0, 2}, {k, 0, 2}]];
>
> dataf = ReadList["C:\\Debug\\ForRegression.txt",
> Number, RecordLists -> True];
>
> datafromfile = Transpose[dataf];
>
> RegResult = Regress[dataf, polynomial, {x, y, z}]
>
> I am getting error
> "Regress::mindata: The number of parameters to be
> estimated is greater than or
> equal to the number of data points.  Subsequent
> results may be misleading.
>
> DesignedRegress::rank: Warning: the rank of the design
> matrix is 25, less \
> than full rank 27. Only 25 of the 27 basis functions
> are needed to provide \
> this fit. Try using a different model or greater
> precision."
>
>
> Kindly help me fix the problem

The first message seems straightforward,without knowing dataf there's  
not much to say.

As for the second message it's not enough that the data points are  
unique, they have to form a design matrix of full rank, hence the  
second message, does your data contain two different responses for  
the same points?

Regards,

Ssezi


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