On 08/04/2023 5:53 p.m., Martin Maechler wrote:
Christophe Dutang
on Sat, 8 Apr 2023 14:21:53 +0200 writes:
> Dear all,
> Using rmultinom() in a stochastic model, I found this function returns
an error message 'NA in probability' for an infinite probability.
> Maybe, a more precise message will be helpful when debugging.
>> rmultinom(1, 3:5, c(1/2, 1/3, Inf))
> Error in rmultinom(1, 3:5, c(1/2, 1/3, Inf)) : NA in probability vector
>> rmultinom(1, 3:5, c(1/2, 1/3, NA))
> Error in rmultinom(1, 3:5, c(1/2, 1/3, NA)) : NA in probability vector
Thank you.
I agree the first ('Inf') should not do what it currently does,
and probably the 2nd one should neither give an error.
Note that in rmultinom, the 'prob' is allowed to be *NOT*
scaled to sum(.) = 1.
Therefore 'Inf' makes sense as the limit (of a sequence) of (a)
very large number(s).
I claim that
rmultinom(1, 3, c(1/2, 1/3, Inf))
should give the same as
rmultinom(1, 3, c(1/2, 1/3, 1e300))
even without a warning,
That case makes sense, but is it worth the effort? Certainly
rmultinom(1, 3, c(1/2, Inf, Inf))
can't give a useful answer because we don't know the relative size of
the two infinities. I imagine the first NA comes from computing
prob/sum(prob), which is c(0, 0, NaN).
Duncan Murdoch
> and OTOH, an NA in prob may return NA (and signal a warning)
> instead of an error.
> For rgeom() or rbinom(), we got a warning for infinite probability :
Yes, but there, prob must be in [0,1] ... so that's somewhat differnt.
>> rbinom(1, 3, Inf)
> [1] NA
> Warning message:
> In rbinom(1, 3, Inf) : NAs produced
>> rbinom(1, 3, NA)
> [1] NA
> Warning message:
> In rbinom(1, 3, NA) : NAs produced
>> rgeom(1, Inf)
> [1] NA
> Warning message:
> In rgeom(1, Inf) : NAs produced
>> rgeom(1, NA)
> [1] NA
> Warning message:
> In rgeom(1, NA) : NAs produced
> Maybe, it could be better to harmonize the behavior for infinite
probability.
> Kind regards, Christophe
>> sessionInfo()
> R version 4.2.3 (2023-03-15)
> Platform: aarch64-apple-darwin20 (64-bit)
> Running under: macOS Ventura 13.2.1
> Matrix products: default
> BLAS:
/Library/Frameworks/R.framework/Versions/4.2-arm64/Resources/lib/libRblas.0.dylib
> LAPACK:
/Library/Frameworks/R.framework/Versions/4.2-arm64/Resources/lib/libRlapack.dylib
> locale:
> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
> attached base packages:
> [1] stats graphics grDevices utils datasets methods base
> loaded via a namespace (and not attached):
> [1] compiler_4.2.3 tools_4.2.3
> -------------------------------------------------
> Christophe DUTANG
> LJK, Ensimag, Grenoble INP, UGA, France
> Web: http://dutangc.free.fr
> ______________________________________________
> R-devel@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
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