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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: -corrtable- available from SSC |

Date |
Fri, 30 Nov 2007 15:46:06 -0000 |

Thanks to Kit Baum, a new module -corrtable- is available from SSC. Stata 8 is required. Use -ssc- to install if interested, and even if not interested. -corrtable- is for presenting correlation matrices as graphical tables: not as "heat maps" or the like, but as tables produced by -graph-, with the possibilities that allows. -corrtable- arose because a colleague was somewhat frustrated in getting a correlation matrix in the form he wanted out of Stata and into his favourite word processor (not a word shall escape me on which that is, but it isn't my own favourite way of producing documents). As often happens, a different approach to get round his problems turned out to be something that might be more generally useful, to me and perhaps others. The basic idea is very simple. Each cell in a correlation matrix is a correlation like say (to 3 d.p.) 0.420 which we could put on a single graph like this: twoway scatteri 1 1 "0.420", ms(none) mlabsize(*7) xscale(r(0 2) off) yscale(r(0 2) off) mlabpos(0) It is unlikely that you would want to do this for an individual correlation, but looping over pairs of variables would give you a matrix of graphs that you can then -combine-. And other modifications then are relatively easy, including formatting with different numbers of decimal places, adding information on sample size (if that differs between correlations) and P-value, changing the font according to the correlation and changing the background colour to indicate different classes. -corrtable- is the result. The help file is quite detailed and lays down all kinds of reservations, not least that this can be slooooooooooooooooooooooowwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww. To repeat another: -corrtable- does not support starring systems such as * ** *** for different levels of significance and I have no intention of implementing any. I don't have, or even want, the power to stop others cloning the program and implementing that, but I decline to do it myself. Most P-values for correlations are not worth much any way insofar, as the assumptions of mutual independence and bivariate normality are often a matter of faith. Also, correlation matrices are almost always much less informative than scatter plot matrices, but you know that anyway. But I shouldn't disparage my own program. I guess some people will enjoy playing with it a bit. If you ever need to give a talk including little correlation matrices, this is a way of going beyond a very mundane table -- and, positively, highlights and patterns in your table can be made clearer without graphamatazz. I showed the results to someone who uses quite different software and was told, "Oh, that would be _very_ fiddly programming in ??????". I am not clear how to quantify that against the few hours I spent on this piece of Stata, but there you are. Nick n.j.cox@durham.ac.uk * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: -corrtable- available from SSC***From:*Phil Schumm <pschumm@uchicago.edu>

**Re: st: -corrtable- available from SSC***From:*Richard Williams <Richard.A.Williams.5@ND.edu>

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