[R] evaluation of the alternative expression in ifelse

[Gabor Grothendieck]

Try:

log(ifelse(x < 0, NaN, x))

or

suppressWarnings(ifelse(x < 0, NaN, log(x)))

or

ifelse(x < 0, NaN, log(pmax(0, x)))



On 6/4/06, Renaud Lancelot <renaud.lancelot at gmail.com> wrote:
> Dear all,
>
> I am trying to avoid the warnings produced by:
>
> > x <- -2:2
> > log(x)
> [1]       NaN       NaN      -Inf 0.0000000 0.6931472
> Warning message:
> production de NaN in: log(x)
>
> I thought that using ifelse would be a solution, but it is not the case:
>
> > ifelse(test = x < 0, yes = NaN, no = log(x))
> [1]       NaN       NaN      -Inf 0.0000000 0.6931472
> Warning message:
> production de NaN in: log(x)
>
> I am aware of the section "Warning" of the help page for ifelse:
> Sometimes it is better to use a construction such as (tmp <- yes;
> tmp[!test] <- no[!test]; tmp), possibly extended to handle missing
> values in test.
>
> However, is there a way to avoid the evaluation of the alternative
> expression in ifelse when the argument test is false ?
>
> Best regards,
>
> Renaud
> --
> Renaud LANCELOT
> Département Elevage et Médecine Vétérinaire (EMVT) du CIRAD
> Directeur adjoint chargé des affaires scientifiques
>
> CIRAD, Animal Production and Veterinary Medicine Department
> Deputy director for scientific affairs
>
> Campus international de Baillarguet
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>
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