# [R] How to manipulate an abitrary dimensioned array.

Mike Meyer mikem at salter-point.com
Fri Oct 28 00:43:05 CEST 2005

```Thanks for the suggestion.
Perhaps I can see how to use apply to get the ratio, but say I also want
to return X[,,,,1] in a general way.  Maybe I am being dense but I just
don't see it --- probably as a result of too much Perl/Python/Java
recently that is clouding my mind.

So can someone suggest a general function that will give me the last
layer of an arbitrary dimensioned array?

Berton Gunter wrote:
> Why doesn't apply() already do what you want?
>
> -- Bert Gunter
> Genentech Non-Clinical Statistics
> South San Francisco, CA
>
> "The business of the statistician is to catalyze the scientific learning
> process."  - George E. P. Box
>
>
>
>
>>-----Original Message-----
>>From: r-help-bounces at stat.math.ethz.ch
>>[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Mike Meyer
>>Sent: Thursday, October 27, 2005 2:50 PM
>>To: r-help at stat.math.ethz.ch
>>Subject: [R] How to manipulate an abitrary dimensioned array.
>>
>>If I have an n1 x n1 x 2 array X I can calculate, say,
>>X[,,1]/X[,,2].
>>
>>If it is a 4 dimensional array then I want to be able to calculate
>>X[,,,1]/X[,,,2], and similarly for higher dimensions.
>>
>>How can I write a function to do this in a general way
>>without having to
>>do a switch for each possible length(dim(X)).  So I want a function g
>>that will take an arbitrary dimensioned array, X, and return
>>X[,,,1]/X[,,,2], etc.   I know how to do this by turning X into a
>>vector, then doing the division, then re-shaping as an array,
>>but that
>>doesn't seem very elegant.
>>
>>What I think I am missing is how to paste/substitute/eval a bunch of
>>commas into an array selection.
>>
>>Thanks, --Mike
>>
>>--
>>Mike Meyer,  Seattle WA
>>
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