performance of apply
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 ------------------------------------------------------+------ Biostatistics : "Never attribute to malice what : Uni of Washington : can be adequately explained by : Box 357232 : incompetence" - Hanlon's Razor : Seattle WA 98195-7232 : : ------------------------------------------------------------ -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-devel-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._