There is another undocumented glitch in sample:
sample(2^31-1,1) => OK
sample(2^31 ,1) => Error
I suppose you could interpret "sampling takes place from '1:x' " to
mean that 1:x is actually generated, but that doesn't work as an
explanation either; on my 32-bit Windows box, 1:(2^29) gives an error,
but sample(2^29,1) works fine.
-s
On Fri, Jan 2, 2009 at 2:18 PM, Wacek Kusnierczyk
<waclaw.marcin.kusnierc...@idi.ntnu.no> wrote:
> xxx wrote:
>> On Fri, Jan 2, 2009 at 10:07 AM, Wacek Kusnierczyk
>> <waclaw.marcin.kusnierc...@idi.ntnu.no> wrote:
>>
>>> ... 'sample' takes a sample of the specified size from the elements of
>>> 'x' using either with or without replacement.
>>>
>>> x: Either a (numeric, complex, character or logical) vector of
>>> more than one element from which to choose, or a positive
>>> integer.
>>>
>>> If 'x' has length 1, is numeric (in the sense of 'is.numeric') and
>>> 'x >= 1', sampling takes place from '1:x'. _Note_ that this
>>> convenience feature may lead to undesired behaviour when 'x' is of
>>> varying length 'sample(x)'. See the 'resample()' example below.
>>> ...
>>> yet the following works, even though x has length 1 and is *not* numeric:...
>>> is this a bug in the code, or a bug in the documentation?
>>>
>>
>> I would guess it's a bug in the documentation.
>>
>>
>
> possibly. looking at the r code for sample, it's clear why
> sample("foo") works:
>
> function (x, size, replace = FALSE, prob = NULL)
> {
> if (length(x) == 1 && is.numeric(x) && x >= 1) {
> if (missing(size))
> size <- x
> .Internal(sample(x, size, replace, prob))
> }
> else {
> if (missing(size))
> size <- length(x)
> x[.Internal(sample(length(x), size, replace, prob))]
> }
> }
>
> what is also clear from the code is that the function has another,
> supposedly buggy behaviour due to the smart behaviour of the : operator:
>
> sample(1.1)
> # 1, not 1.1
>
> this is consistent with
>
> "
> If 'x' has length 1, is numeric (in the sense of 'is.numeric') and
> 'x >= 1', sampling takes place from '1:x'.
> "
>
> due to the downcast performed by the colon operator, but not with
>
> "
> x: Either a (numeric, complex, character or logical) vector of
> more than one element from which to choose, or a positive
> integer.
> "
>
> both from ?sample. tfm is seemingly wrong wrt. the implementation, and
> i find sample(1.1) returning 1 a design flaw. (i guess the note "_Note_
> that this convenience feature may lead to undesired behaviour when 'x'
> is of varying length 'sample(x)'." is supposed to explain away such cases.)
>
> vQ
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
