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matrixStats: Extend to arrays too (Was: Re: Suggestion: Adding quick rowMin and rowMax functions to base package)

In S+ we chose to just append the 's' instead of making
everyone worry about the vagarities of English spelling
and pluralization rules.  We also have 'groupAnys' and
'igroupAnys' (and should have {row,col}Anys, but we don't).

The 'igroup<Summarys>' family of functions in S+ is to the
'group<Summarys>' family as 'tabulate' is to 'table':  it
requires that the grouping variable be an integer in the
range 1:numGroups and in return gives fast results.

Having a similar family of functions for general arrays
would be nice also, but I think that specialized row* and col*
functions are good to have: data.frames only have rows and
columns and I can never remember the MARGIN number conventions
of apply and sweep.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com