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Re: st: RE: RE: looping / refering to multiple variables
From
Maarten Buis <[email protected]>
To
[email protected]
Subject
Re: st: RE: RE: looping / refering to multiple variables
Date
Thu, 6 Oct 2011 11:56:40 +0200
2011/10/6 Nick Cox <[email protected]>:
> gen P_nt = 0
> foreach i of global code {
> replace P_nt = P_nt + cond(missing(l_avgp`i'), 0, l_avgp`i') * ///
> cond(missing(exp_share`i'), 0, exp_share`i')
> }
It is probably safer to start with -gen double P_nt = 0-, since this
is an intermediate computation and you could easily end up adding
numbers of very different sizes, which can lead to precision problems.
See, e.g. page 557 of Gould (2006)
William Gould (2006) Mata matters: Precision. The Stata Journal, 6(4): 550-560.
<http://www.stata-journal.com/article.html?article=pr0025>
Hope this helps,
Maarten
--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany
http://www.maartenbuis.nl
--------------------------
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