lapply(mapply(lapply(...))), along with making a vector out of a matrix then making a matrix out of it again seems like a pretty long-winded way of doing what is done by lapply(seq_along(X), function(i)tt[i,] %*% X[[i]]) or mapply(`%*%`, split(tt,row(tt))[1:3], X, SIMPLIFY=FALSE)
(The example datasets are odd - why doesn't tt have the same number of rows as X has matrices?) Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On > Behalf > Of arun > Sent: Sunday, November 11, 2012 10:41 AM > To: Clemontina Davenport > Cc: R help > Subject: Re: [R] Multiplying elements of a list by rows of a matrix > > Hi, > In this case, you could try: > > res<-lapply(mapply(c,X,lapply(data.frame(t(tt[1:3,])),function(x) > x),SIMPLIFY=FALSE),function(x) x[13:16]%*% matrix(x[1:12],ncol=3) ) > > res > > #[[1]] > # [,1] [,2] [,3] > #[1,] 14.27 16.65 10.12 > > #[[2]] > # [,1] [,2] [,3] > #[1,] 10.14 5.17 18.28 > # > #[[3]] > # [,1] [,2] [,3] > #[1,] 22.66 10.34 8.31 > > > A.K. > > > ----- Original Message ----- > From: Clemontina Davenport <ckale...@ncsu.edu> > To: r-help@r-project.org > Cc: > Sent: Sunday, November 11, 2012 11:33 AM > Subject: [R] Multiplying elements of a list by rows of a matrix > > Hi all, > I have the following code: > > set.seed(1) > x1 <- matrix(sample(1:12), ncol=3) > x2 <- matrix(sample(1:12), ncol=3) > x3 <- matrix(sample(1:12), ncol=3) > X <- list(x1,x2,x3) > tt <- matrix(round(runif(5*4),2), ncol=4) > > Is there a way I can construct a new list where > newlist[[i]] = tt[i,] %*% X[[i]] > without using a for loop? Each element of newlist will be 3 x 1 vector. > > Thanks > -- > Tina Alexander > > ______________________________________________ > 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.
