Hi, Suppose I I wish to run lm( y ~ x + z + log(w) ) where w assumes non-negative values. A problem arises when w=0, as log(0) = -Inf, and R doesn't accept that (as it "accepts" NA). Is there a way to tell R to do with -Inf the same it does with NA, i.e, to ignore it? ( Otherwise I have to do something like w[w==0] <- NA which doesn't hurt, but might be a bit incovenient sometimes.) Thanks in advance. Dimitri
you could use:
lm( y ~ x + z + log(w), subset = w > 0)
I hope it helps.
Best,
Dimitris
----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://www.med.kuleuven.be/biostat/
http://www.student.kuleuven.be/~m0390867/dimitris.htm
----- Original Message -----
From: "Dimitri Szerman" <dimitrijoe at ipea.gov.br>
To: "R-Help" <r-help at stat.math.ethz.ch>
Sent: Tuesday, October 25, 2005 4:47 PM
Subject: [R] Inf in regressions
> Hi,
>
> Suppose I I wish to run
>
> lm( y ~ x + z + log(w) )
>
> where w assumes non-negative values. A problem arises when w=0, as
> log(0)
> = -Inf, and R doesn't accept that (as it "accepts" NA). Is
there a
> way to
> tell R to do with -Inf the same it does with NA, i.e, to ignore it?
> (
> Otherwise I have to do something like
>
> w[w==0] <- NA
>
> which doesn't hurt, but might be a bit incovenient sometimes.)
>
> Thanks in advance.
>
> Dimitri
>
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Actually, R does not accept NA. First, the action is from lm and not from the R base, and second, NAs are in fact deleted and not accepted. Function lm() has a na.action argument which is by default na.omit. You could easily make na_and_inf.omit and use it. You could also use subset=(w > 0). The help pages are your friends here. On Tue, 25 Oct 2005, Dimitri Szerman wrote:> Suppose I I wish to run > > lm( y ~ x + z + log(w) ) > > where w assumes non-negative values. A problem arises when w=0, as log(0) > = -Inf, and R doesn't accept that (as it "accepts" NA). Is there a way to > tell R to do with -Inf the same it does with NA, i.e, to ignore it? ( > Otherwise I have to do something like > > w[w==0] <- NA > > which doesn't hurt, but might be a bit incovenient sometimes.)-- Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595