HI, set.seed(15) mat1<-matrix(sample(1:1000000,8000000,replace=TRUE),nrow=8000) w <- 1/1:8000 system.time(diag(w)%*%mat1) # user system elapsed # 54.235 0.444 54.792 system.time(sweep(mat1,MARGIN=1,w,`*`) ) # user system elapsed # 0.220 0.044 0.265 system.time(t(sapply(seq_along(w),function(i) mat1[i,]*w[i]))) # user system elapsed # 0.288 0.048 0.337 system.time(sapply(seq_along(w),function(i) mat1[i,]*w[i])) #without the transpose, Rui's method is better # user system elapsed # 0.180 0.028 0.207 system.time(do.call(rbind,lapply(seq_along(w),function(i) mat1[i,]*w[i]))) # user system elapsed # 0.228 0.024 0.250 system.time(lapply(seq_along(w),function(i) mat1[i,]*w[i])) # user system elapsed # 0.140 0.000 0.139
A.K. ----- Original Message ----- From: Rui Barradas <ruipbarra...@sapo.pt> To: frespider <frespi...@hotmail.com> Cc: r-help@r-project.org Sent: Friday, November 16, 2012 2:45 PM Subject: Re: [R] Multiple Vector with matrix in R Hello, Try the following. t(sapply(seq_along(w), function(i) mat1[i,]*w[i])) Hope this helps, Rui Barradas Em 16-11-2012 16:34, frespider escreveu: > Hi > > Can someone show me an easy way to multiple a weighted vector with an > matrix? > > example below > mat1<-matrix(sample(1:100,80,replace=TRUE),ncol=8) > w <- 1/1:10 > > I want the first element in w to be multiplied by the first row of mat1 and > 2nd element in w to be multiplied with the 2nd row and so on. > > I have huge matrix is there an easy way other than diag(w)%*%mat1 > > Thanks > > > > -- > View this message in context: > http://r.789695.n4.nabble.com/Multiple-Vector-with-matrix-in-R-tp4649764.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
