[R] curious about dimension of 'apply' output when MARGIN=1

Benjamin Tyner btyner at stat.purdue.edu
Thu Jan 18 15:16:27 CET 2007

Thanks to all for your insightful comments. I must admit I was unaware 
of the application to arrays.


Prof Brian Ripley wrote:
> Or that the vision of the original designer was not limited to 
> matrices. It just so happens that in this example the replacement is a 
> single dimension the same size as the single margin used.  That's 
> atypical, and normally the result dimension has no connection to the 
> margin.  The design is to put the result dimension first, and the 
> first item in the 'seealso' list is aperm().
> To my mind the only general solutions are to put the result dimension 
> first or last.  I would have used last, but using first is slightly 
> more efficient for the reason Pat gives.
> apply() is for arrays, operating over one or more margins with a 
> function returning a 'scalar', vector or array result.  Perhaps any 
> 'lazy'-ness / limit of vision is not in handling array results as well 
> as might be possible.

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