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st: pwcorr(2)


From   Kit Baum <baum@bc.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: pwcorr(2)
Date   Thu, 11 Dec 2008 20:33:21 -0500

< >
In the "users rush in where StataCorp fears to tread" department, there is now a routine -pwcorr2- available on SSC. It is official - pwcorr- with an added feature: three matrices are returned, containing correlations (r(C), like -correlate-)), sample sizes (r(Cn)) and significance levels (r(Cp)).

Nick Cox raises some very good points suggesting why StataCorp may have failed to include this feature in official -pwcorr-. The matrices returned should be used with caution; in particular, one should not think of r(C) as being a 'correlation matrix' of the data, in the sense that one may transform a variance-covariance matrix calculated over N observations into a correlation matrix. But as a descriptive tool, one may often want to calculate pairwise correlations over disparate samples (particularly useful in my experience in time-series data), and it is cumbersome to calculate them one pair at a time with - correlate-. -pwcorr2- circumvents that limitation, but should be used with caution.

-ssc describe pwcorr2-  for details.


Kit Baum, Boston College Economics and DIW Berlin
http://ideas.repec.org/e/pba1.html
An Introduction to Modern Econometrics Using Stata:
http://www.stata-press.com/books/imeus.html


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