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Re: st: tetrachoric correlation


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: tetrachoric correlation
Date   Wed, 15 Nov 2006 17:20:20 +0000 (GMT)

--- prneiva <prneiva@terra.com.br> wrote:
> When I write  matrix list r(Rho), the answer is matrix r(Rho) not
> found. 

Did you type -matrix list r(Rho)- after typing -tetrachoric varlist,
whatever option-? Better yet, did you copy the example I gave you and
tried that. That example should not give that error message, at least
it didn't gave me that error message.
 
> When I use the following procedure:
> matrix C = r(Rho)
> local n = r(N)
> factormat C, n(`n')
> 
> the answer is: matrix C has missing values. 
> 
> I donīt know what is happening, since the codebook shows that there
> is no missing values. 

Missing values in your data isn't the issue here, the missing values
are in the matrix. -factormat- needs all pairwise correlations, and if
one is missing it complaints. You can still get a complete correlation
matrix if you have missing data. One way to see what's going on is to
type -matrix list C-. 

Actually, if you are using real data I'd be worried if I did not have
missing values. It's not that I like them, but I know that real data
has them and that if I can't find them someone else has done something
I might not like, like just delete any case with a missing value or
impute it with the mean.

HTH,
Maarten

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting adress:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------

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