[R] sample within groups-slight problem

[Jean-Christophe BOUËTTÉ]

Hi there,
in the third case you get sample(5) which is exactly what you asked for.

from ?sample:
"If x has length 1, is numeric (in the sense of is.numeric) and x >=
1, sampling via sample takes place from 1:x. Note that this
convenience feature may lead to undesired behaviour when x is of
varying length in calls such as sample(x). See the examples. "

2011/9/6 Jack Siegrist <jacksie at eden.rutgers.edu>:
> I want to sample within groups, and when a group has only one associated
> number to just return that number.
>
> If I use this code:
>
> groups <- c(1, 2, 2, 2, 3)
> numbers <- 1:5
> tapply(numbers, groups, FUN = sample)
>
> I get the following output:
>
>>  groups <- c(1, 2, 2, 2, 3)
>>  numbers <- 1:5
>>  tapply(numbers, groups, FUN = sample)
> $`1`
> [1] 1
>
> $`2`
> [1] 3 2 4
>
> $`3`
> [1] 2 3 5 1 4
>
> Can someone tell me why the $'3' result samples all of the numbers and how
> to prevent it from doing so? I want the output for the $'3' part to just be
> 5 in this example.
>
> Thanks for your help.
>
>
>> sessionInfo()
> R version 2.11.1 (2010-05-31)
> i386-pc-mingw32
>
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