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Re: st: R: Log of nonpositive numbers


From   "Austin Nichols" <austinnichols@gmail.com>
To   statalist@hsphsun2.harvard.edu
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
arguments.
  ssc inst transint
  help transint
has a useful discussion of alternatives.

On Sat, Mar 29, 2008 at 4:59 PM, ucb_gal <ucb_gal@yahoo.com> 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 <carlo.lazzaro@tin.it>
>  To: statalist@hsphsun2.harvard.edu
>  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: owner-statalist@hsphsun2.harvard.edu
>  [mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di ucb_gal
>  Inviato: sabato 29 marzo 2008 6.57
>  A: statalist@hsphsun2.harvard.edu
>  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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