[R] Array analogue of row and col

[Tony Plate]

slice.index() in base

On 4/2/2013 9:53 AM, Enrico Bibbona wrote:
> Great!
> Thanks a lot, Enrico
>
>
> 2013/4/2 Duncan Murdoch <murdoch.duncan at gmail.com>
>
>> On 02/04/2013 6:36 AM, Enrico Bibbona wrote:
>>
>>> Is there any function that extends to multidimentional arrays the
>>> functionalities of "row" and "col" which are just defined for matrices?
>>> Thanks, Enrico Bibbona
>>>
>> Not as far as I know, but there are a lot of functions in packages.
>>
>> You could write your own something like this.  I've skipped any error
>> checking; you'll want to add that.
>>
>> indices <- function(a, which) {
>>    d <- dim(a)
>>    prod_before <- prod(d[seq_len(which-1)])
>>    result <- rep(seq_len(d[which]), each=prod_before,  length.out = prod(d))
>>    dim(result) <- d
>>    result
>> }
>>
>> Then indices(a, 1) gives an array of the same shape as a where entry i, j,
>> k, ... is i, indices(a, 2) has entry i,j,k, ... equal to j, etc.
>>
>> Duncan Murdoch
>>
>>
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