Re: [pdl-stats] Detecting cross correlation in logistic regression independent parms.

[Maggie X. <mag...@us...>]

In the context of logistic regression, by cross correlation you mean Pearson
correlation matrix for a set of variables? The function corr_table() in
PDL::Stats::Basic can give you that. You can also calculate it from
covariance matrix by dividing the covariance with the product of of the
standard deviations of the two variables you are correlating with.


Best,
Maggie


On Mon, Apr 25, 2011 at 10:54 PM, <dw...@em...> wrote:

>
> I apologize in advance if this is obvious. I'm an ex-scientist, from a
> generation  for which Bevington's "Data Reduction
> and Error Analysis in the Physical Sciences" was our Bible. To determine
> cross correlation of a fit, we'd extract
> the covariance matrix from our fitters, do some math presto magico things,
> and then could determine if
> we were fitting cross correlated data (then drop one of the correlated
> coefficients from our models..).
>
>  I'm working with PDL::Stats logistic method. Works great, but haven't a
> clue how to detect cross correlation.
> I suspect the "how" is obvious to a stats major, but not to an
> ex-biochemist like me. The underlying fitter
> returns $cov, but no clue how to get to it.
>
>  Any help appreciated.
>
>  Sincerely,
>
>  David Myers.
>
>
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