[R] Combinations

Prof Brian D Ripley ripley at stats.ox.ac.uk
Tue Dec 14 14:11:00 CET 1999

On Tue, 14 Dec 1999, Chuck Cleland wrote:

>   Why not use expand.grid() and subscript away any unwanted rows?

How are you going to work out which ones are unwanted, efficiently? And for
moderately sized problems you will run out of space in expand.grid, as
there are many more k-tuples than combinations. (More than k! times
as many.)

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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