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 <[email protected]> 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 <[email protected]>
> To: [email protected]
> 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: [email protected]
> [mailto:[email protected]] Per conto di ucb_gal
> Inviato: sabato 29 marzo 2008 6.57
> A: [email protected]
> 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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