From: Marcel Wolbers (wolbers@stat.math.ethz.ch)
Date: Thu 19 Jul 2001 - 16:35:41 EST
Message-id: <15190.32701.295873.994634@gargle.gargle.HOWL>
>> My question: Are there equivalents to colSums in R?
I don't think there are functions for doing this, but you can speed
up things a lot by using matrix operations instead of apply if
this is possible:
> x <- matrix(rnorm(1E5),ncol=100)
> system.time(tmp1 <- apply(x,2,sum))
[1] 0.04 0.01 0.05 0.00 0.00
> system.time(tmp2 <- c(rep(1,nrow(x))%*%x))
[1] 0.01 0.00 0.01 0.00 0.00
> all.equal(tmp1,tmp2)
[1] TRUE
Yours,
Marcel Wolbers
-- Marcel Wolbers, LEO C14, Seminar for Statistics, ETH Zurich CH-8092 Zurich, Switzerland; phone: (01) 632 2252 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help 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-help-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
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