[R] rep() fails at times=0.29*100

[Henrik Bengtsson]

FYI,

> (0.29*100) < 29
[1] TRUE

See R FAQ 7.31 for why.

/Henrik

On Tue, Apr 9, 2013 at 9:11 AM, Jorge Fernando Saraiva de Menezes
<jorgefernandosaraiva at gmail.com> wrote:
> Dear list,
>
> I have found an unusual behavior and would like to check if it is a
> possible bug, and if updating R would fix it. I am not sure if should post
> it in this mail list but I don't where is R bug tracker. The only mention I
> found that might relate to this is "If times is a computed quantity it is
> prudent to add a small fuzz." in rep() help, but not sure if it is related
> to this particular problem
>
> Here it goes:
>
>> rep(TRUE,29)
>  [1] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
> TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
> [28] TRUE TRUE
>> rep(TRUE,0.29*100)
>  [1] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
> TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
> [28] TRUE
>> length(rep(TRUE,29))
> [1] 29
>> length(rep(TRUE,0.29*100))
> [1] 28
>
> Just to make sure:
>> 0.29*100
> [1] 29
>
> This behavior seems to be independent of what is being repeated (rep()'s
> first argument)
>> length(rep(1,0.29*100))
> [1] 28
>
> Also it occurs only with the 0.29.
>> length(rep(1,0.291*100))
> [1] 29
>> for(a in seq(0,1,0.01)) {print(sum(rep(TRUE,a*100)))} #also shows correct
> values in values from 0 to 1 except for 0.29.
>
> I have confirmed that this behavior happens in more than one machine
> (though I only have session info of this one)
>
>
>> sessionInfo()
> R version 2.15.3 (2013-03-01)
> Platform: x86_64-w64-mingw32/x64 (64-bit)
>
> locale:
> [1] LC_COLLATE=Portuguese_Brazil.1252  LC_CTYPE=Portuguese_Brazil.1252
>  LC_MONETARY=Portuguese_Brazil.1252
> [4] LC_NUMERIC=C                       LC_TIME=Portuguese_Brazil.1252
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> other attached packages:
> [1] spatstat_1.31-1 deldir_0.0-21   mgcv_1.7-22
>
> loaded via a namespace (and not attached):
> [1] grid_2.15.3     lattice_0.20-13 Matrix_1.0-11   nlme_3.1-108
>  tools_2.15.3
>
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>
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