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Re: st: About taking log on zero values
From
Maarten Buis <[email protected]>
To
[email protected]
Subject
Re: st: About taking log on zero values
Date
Thu, 20 Feb 2014 16:48:51 +0100
On Thu, Feb 20, 2014 at 4:16 PM, Alfonso Sánchez-Peñalver wrote:
> In any case, if possible the best possible solution would be to estimate the values that ln(sales) would take for those zeros using either a Tobit or a Heckman sample selection model.
This might work if we were talking about an dependent variable (though
in that case I would just use a glm with a log link). However, we are
talking about an independent variable. What should happen with the 0s
depends on the functional form of the relationship between sales (the
independent variable, which Sebastian wants to log) and y (the
dependent variable). A Tobit or a Heckman are not tools for
determining such a functional form, and can thus not be a solution to
this problem.
-- Maarten
---------------------------------
Maarten L. Buis
WZB
Reichpietschufer 50
10785 Berlin
Germany
http://www.maartenbuis.nl
---------------------------------
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