Re: [R] Faster matrix operation?
On 1 June 2010 11:34, Peter Ehlers wrote: > Or, for a very slight further reduction in time in > the case of larger matrices/vectors: > > as.vector(tcrossprod(V, xyzs)) > > I mention this merely to remind new users of the > excellent speed of [t]crossprod(). > > -Peter Ehlers Thanks, I've been using t(x)%*%y for several years now, and had never found out there was a faster and more straight-forward function for this. Perhaps a link to [t]crossprod could be added on the help page for ?"%*%". Best, baptiste __ 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.
Re: [R] Faster matrix operation?
On 2010-06-01 0:16, bill.venab...@csiro.au wrote: xyzs<- matrix(rnorm(3*10,0,1),ncol=3) V<- c(2,3,4) system.time(vx<- apply(t(xyzs) * V, 2 ,sum)) user system elapsed 1.060.021.08 system.time(wx<- as.vector(xyzs %*% V)) user system elapsed 0 0 0 all.equal(vx, wx) [1] TRUE Or, for a very slight further reduction in time in the case of larger matrices/vectors: as.vector(tcrossprod(V, xyzs)) I mention this merely to remind new users of the excellent speed of [t]crossprod(). -Peter Ehlers ? -Original Message- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Remko Duursma Sent: Tuesday, 1 June 2010 4:04 PM To: r-help@r-project.org Subject: [R] Faster matrix operation? Dear R-helpers, I have a three-column matrix with lots of rows: xyzs<- matrix(rnorm(3*10,0,1),ncol=3) # And I am multiplying it with some vector V, and summing the rows (columns after t()) in this way: V<- c(2,3,4) system.time(vx<- apply(t(xyzs) * V, 2 ,sum)) Ok, this does not take long (0.9 sec on my machine), but I have to do this lots of times, with frequently larger matrices. Is there a way to significantly speed this up, apart from writing it in Fortran or C and calling it from within R (which is what I am planning unless there is an alternative)? thanks, Remko __ 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.
Re: [R] Faster matrix operation?
> xyzs <- matrix(rnorm(3*10,0,1),ncol=3) > > V <- c(2,3,4) > system.time(vx <- apply(t(xyzs) * V, 2 ,sum)) user system elapsed 1.060.021.08 > > system.time(wx <- as.vector(xyzs %*% V)) user system elapsed 0 0 0 > all.equal(vx, wx) [1] TRUE > ? -Original Message- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Remko Duursma Sent: Tuesday, 1 June 2010 4:04 PM To: r-help@r-project.org Subject: [R] Faster matrix operation? Dear R-helpers, I have a three-column matrix with lots of rows: xyzs <- matrix(rnorm(3*10,0,1),ncol=3) # And I am multiplying it with some vector V, and summing the rows (columns after t()) in this way: V <- c(2,3,4) system.time(vx <- apply(t(xyzs) * V, 2 ,sum)) Ok, this does not take long (0.9 sec on my machine), but I have to do this lots of times, with frequently larger matrices. Is there a way to significantly speed this up, apart from writing it in Fortran or C and calling it from within R (which is what I am planning unless there is an alternative)? thanks, Remko - Remko Duursma Research Lecturer Centre for Plants and the Environment University of Western Sydney Hawkesbury Campus Richmond NSW 2753 Dept of Biological Science Macquarie University North Ryde NSW 2109 Australia Mobile: +61 (0)422 096908 www.remkoduursma.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] Faster matrix operation?
Dear R-helpers, I have a three-column matrix with lots of rows: xyzs <- matrix(rnorm(3*10,0,1),ncol=3) # And I am multiplying it with some vector V, and summing the rows (columns after t()) in this way: V <- c(2,3,4) system.time(vx <- apply(t(xyzs) * V, 2 ,sum)) Ok, this does not take long (0.9 sec on my machine), but I have to do this lots of times, with frequently larger matrices. Is there a way to significantly speed this up, apart from writing it in Fortran or C and calling it from within R (which is what I am planning unless there is an alternative)? thanks, Remko - Remko Duursma Research Lecturer Centre for Plants and the Environment University of Western Sydney Hawkesbury Campus Richmond NSW 2753 Dept of Biological Science Macquarie University North Ryde NSW 2109 Australia Mobile: +61 (0)422 096908 www.remkoduursma.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.
