From thomas@biostat.washington.edu  Fri May 29 17:14:36 1998
From: thomas@biostat.washington.edu (Thomas Lumley)
Date: Fri, 29 May 1998 09:14:36 -0700 (PDT)
Subject: performance of apply
In-Reply-To: <6rlnrldvez.fsf@verdi.stat.wisc.edu>
Message-ID: <Pine.LNX.3.96.980529090735.23645A-100000@buffy>

On 29 May 1998, Douglas Bates wrote:

> Andreas Weingessel <Andreas.Weingessel@ci.tuwien.ac.at> writes:
> 
> > I noticed that apply is VERY SLOW when applied to a "large"
> > dimension as for example when computing the row sums of a matrix with
> > thousands of rows.
> > 
> 

> 
> We should keep in mind when looking at these tables that the maximum
> time on the size 10000 case is about 2 minutes.  If the computation is
> worth doing it may be worth waiting 2 minutes for the result.  I
> remember the days of running S version 2 (i.e. the version before "New
> S") on a Vax-11/750.  This sort of computation could take many, many
> hours on the only computer in the department so relative differences
> in speed for different methods were a lot more important.  One got
> used to rephrasing computations in "efficient" ways.  Today I think
> that clarity is usually more important than efficiency.

One of the really nice things about R is that you _don't_ have to use
apply to get loops to run in reasonable time, since for most non-Lisp
people for() is simpler than apply(). 


Thomas Lumley
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performance of apply
Thomas Lumley