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Re: st: R: Log of nonpositive numbers

From   "Austin Nichols" <>
Subject   Re: st: R: Log of nonpositive numbers
Date   Sat, 29 Mar 2008 23:09:24 -0400

No, it would not be okay.  You might instead pick an alternative
transformation that is similar to the log but allows for nonpositive
  ssc inst transint
  help transint
has a useful discussion of alternatives.

On Sat, Mar 29, 2008 at 4:59 PM, ucb_gal <> wrote:
> With regards to the wealth variable, I have a number of cases that are substantially negative (with net worth less than negative $50k).  Would adding a constant as large at 100k be OK?
>  ----- Original Message ----
>  From: Carlo Lazzaro <>
>  To:
>  Sent: Saturday, March 29, 2008 1:45:56 AM
>  Subject: st: R: Log of nonpositive numbers
>  Dear Ucb_gal,
>  a tempative answer might be to add a little constant to your zeros, in order
>  to make natural log transformation feasible. However, this trick will give
>  you back <0 values.
>  Kind Regards,
>  Carlo
>  -----Messaggio originale-----
>  Da:
>  [] Per conto di ucb_gal
>  Inviato: sabato 29 marzo 2008 6.57
>  A:
>  Oggetto: st: Log of nonpositive numbers
>  Hi,
>  I've seen this question asked a few other times, but I'm still a little
>  unclear on what the considerations are in thinking this through.
>  I'm running logistic regressions with the log of income and wealth as
>  independent variables.  I've seen this done often enough that I didn't
>  really think twice about it.  But then I realized that while I don't have a
>  ton of cases with exact 0 values in either variable, I do have a number of
>  cases with negative wealth.  And all of these show up as missing now.
>  Am I mistaken in thinking that I've seen studies that use the log of income
>  as predictors??
>  Thanks!
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