[R] building a subscript programatically

[Comcast]

Leaving the indices empty should give you what I'm guessing you want/expect.

x[,,2]    #.  TRUE would also work, just not in a list.

David.

On Nov 1, 2011, at 6:14 PM, Ernest Adrogué <nfdisco at gmail.com> wrote:

> Hi,
> 
> On ocasion, you need to subscript an array that has an arbitrary
> (ie. not known in advance) number of dimensions. How do you deal with
> these situations?
> It appears that it is not possible use a list as an index, for
> instance this fails: 
> 
>> x <- array(NA, c(2,2,2))
>> x[list(TRUE,TRUE,2)]
> Error in x[list(TRUE, TRUE, 2)] : invalid subscript type 'list'
> 
> The only way I know is using do.call() but it's rather ugly. There
> must be a better way!!
> 
>> do.call('[', c(list(x), TRUE, TRUE, 2))
>     [,1] [,2]
> [1,]   NA   NA
> [2,]   NA   NA
> 
> Any idea?
> 
> Regards,
> Ernest
> 
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