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Re: st: About taking log on zero values


From   jose maria pacheco de souza <[email protected]>
To   [email protected]
Subject   Re: st: About taking log on zero values
Date   Fri, 21 Feb 2014 10:22:50 -0300

Em 21/02/2014 10:17, Maarten Buis escreveu:
On Fri, Feb 21, 2014 at 1:53 PM, jose maria pacheco de souza  wrote:
It would be very useful if someone  could make an organized summary of the
sugestions.

Nick started out with a well organized and large set of sugestions and
considerations <http://www.stata.com/statalist/archive/2014-02/msg00790.html>

To that I added the option of creating an indicator variable for x=0,
set x at the smallest non-zero value, take the log of that x and add
both the log and the indicator variable.
<http://www.stata.com/statalist/archive/2014-02/msg00826.html> and
that idea was independetly repeated by Daniel Feenberg
<http://www.stata.com/statalist/archive/2014-02/msg00874.html>.

Alternative transformations that don't have a problem with x=0 were
proposed by Mark Schaffer
<http://www.stata.com/statalist/archive/2014-02/msg00837.html> and
Nick Cox <http://www.stata.com/statalist/archive/2014-02/msg00848.html>.

Alfonso Sánchez-Peñalver suggested using Tobit or Heckman models to
predict alternative values for the 0s here:
<http://www.stata.com/statalist/archive/2014-02/msg00845.html>.

Hope this helps,
Maarten

Maarten:
Very good.
Thank you.

josé maria

--
Jose Maria Pacheco de Souza
Professor Titular (aposentado), Professor Senior
Departamento de Epidemiologia/Faculdade de Saude Publica, USP
Av. Dr. Arnaldo, 715
01246-904  -  S. Paulo/SP - Brasil
fone (11)3768-8612
www.fsp.usp.br/~jmpsouza
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