Re: st: About taking log on zero values

[Maarten Buis <maartenlbuis@gmail.com>]

On Fri, Feb 21, 2014 at 1:53 PM, jose maria pacheco de souza  wrote:
> It would be very useful if someone  could make a 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 L. Buis
WZB
Reichpietschufer 50
10785 Berlin
Germany

http://www.maartenbuis.nl
---------------------------------

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