On Thu, 27 Dec 2012 22:03:19 -0800 arun <smartpink...@yahoo.com> wrote:
> HI, > > Not sure if this is what you wanted: > set.seed(14) > Z<-array(sample(1:100,80,replace=TRUE),dim=c(5,2,8)) > set.seed(21) > Y<-matrix(sample(1:40,40,replace=TRUE),nrow=8) > do.call(cbind,lapply(seq_len(dim(Z)[1]),function(i) Z[i,,]%*%Y[,i])) > # [,1] [,2] [,3] [,4] [,5] > #[1,] 5065 6070 12328 11536 13678 > #[2,] 6152 9878 11161 13777 7991 Yes, this does it, many thanks! Ranjan > > > > > ----- Original Message ----- > From: Ranjan Maitra <maitra.mbox.igno...@inbox.com> > To: r-help@r-project.org > Cc: > Sent: Friday, December 28, 2012 12:33 AM > Subject: [R] efficiently multiply different matrices in 3-d array with > different vectors? > > Hello, > > I have been wondering of an efficient way to do this: > > I have an n x m x p array Z and a p x n matrix Y. > > I want to multiply each of the n matrices with the corresponding column > vector of Y. > > In other words, I am wanting to matrix multiply: > > Z[i, ,] %*% Y[, i] > > which will give me a (two-dimensional) array or matrix of dimension n x > p with the i'th row storing the above. > > Any pointers on an efficient way of doing this? I considered using > apply, but was not successful. > > Many thanks again and best wishes, > Ranjan > > > > -- > Important Notice: This mailbox is ignored: e-mails are set to be > deleted on receipt. For those needing to send personal or professional > e-mail, please use appropriate addresses. > > ____________________________________________________________ > FREE ONLINE PHOTOSHARING - Share your photos online with your friends and > family! > Visit http://www.inbox.com/photosharing to find out more! > > ______________________________________________ > 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. > -- Important Notice: This mailbox is ignored: e-mails are set to be deleted on receipt. For those needing to send personal or professional e-mail, please use appropriate addresses. ____________________________________________________________ GET FREE 5GB EMAIL - Check out spam free email with many cool features! Visit http://www.inbox.com/email to find out more! ______________________________________________ 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.
