[R] [newbie] return index(s) for value?

[Uwe Ligges]

On 12.05.2013 00:35, Tom Roche wrote:
>
> Is there a function 'foo' such that, given an array and a value, iff
> the value is present in the array, it returns the index(s) of the
> value? E.g.,
>
>> matrix(1:9, nrow=3) -> grid
>> grid
>       [,1] [,2] [,3]
> [1,]    1    4    7
> [2,]    2    5    8
> [3,]    3    6    9
>> foo(grid, median(grid))
> [1] c(2,2)

which(grid==median(grid), arr.ind=TRUE)

Uwe Ligges

>
> I'm sure I could code this with nested loops, but am nearly as sure
> that this functionality must already exist in R ... since there's so
> much functionality already in R !-)
>
> Apologies if this is a FAQ, but a fair amount of googling via
> rseek.org is not finding an answer (probably because I'm not using the
> correct search terms). Feel free (in fact, be encouraged :-) to reply
> directly to me as well as to the list (I'm on the digest, which gets
> huge).
>
> TIA, Tom Roche <Tom_Roche at pobox.com>
>
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