[R] Base function for flipping matrices

[Hadley Wickham]

> Your request is reminding me of the analysis of aray functions in Philip S
> Abrams dissertation
> http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-r-114.pdf
> AN APL MACHINE
>
> The section that starts on page 17 with this paragraph is the one that
> immediately applies
>
> C. The Standard Form for Select Expressions
>
> In this section the selection operators considered are take, drop, reversal,
> transpose, and subscripting by scalars or _J-vectors. Because of the
> similarity
> among the selection operators, we might expect that an expression consisting
> only
> of selection operators applied to a single array could be expressed
> equivalently in
> terms of some simpler set of operators. This expectation is fulfilled in the
> standard form for select expressions, to be discussed below.

That's fantastic - thanks for the pointer. One thing I'd like to do
with the plyr package is generate a natural (and minimal) set of
operators for data frames in a similar way APL did for arrays.

Hadley

-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/