Hi, What is the elegant script to divide the columns of a matrix by the respective position of a vector elements? m=rbind(c(6,4,2),c(3,2,1)) v= c(3,2,1) res= 6/3 4/2 2/1 3/3 2/2 1/1 this is correct mat2 = NULL for (i in 1: ncol(m)) mat2 = cbind(mat2, m[,i]/ v[i]) but how to do more compact and elegant with for ex do.call? Many thanks Carol [[alternative HTML version deleted]]
You don't need do.call:> t(t(m)/v)[,1] [,2] [,3] [1,] 2 2 2 [2,] 1 1 1> t(apply(m, 1, function(x) x/v))[,1] [,2] [,3] [1,] 2 2 2 [2,] 1 1 1 ------------------------------------- David L Carlson Department of Anthropology Texas A&M University College Station, TX 77840-4352 -----Original Message----- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of carol white Sent: Wednesday, May 14, 2014 9:52 AM To: r-help at stat.math.ethz.ch Subject: [R] matrix column division by vector Hi, What is the elegant script to divide the columns of a matrix by the respective position of a vector elements? m=rbind(c(6,4,2),c(3,2,1)) v= c(3,2,1) res= 6/3?? 4/2? 2/1 ??????? 3/3?? 2/2 ?? 1/1 this is correct? mat2 = NULL for (i in 1: ncol(m)) ??? mat2 = cbind(mat2, m[,i]/ v[i]) but how to do more compact and elegant with for ex do.call? Many thanks Carol [[alternative HTML version deleted]]
Please post in plain text... your email is getting distorted and hard to read by the HTML. I don't know how to use do.call for this, but when you understand how vectors recycle and matrices and arrays are laid out in memory (read the Introduction to R document if not) then the following comes to mind: mat2 <- m / matrix( v, ncol=ncol(m), nrow=nrow(m), byrow=TRUE ) --------------------------------------------------------------------------- Jeff Newmiller The ..... ..... Go Live... DCN:<jdnewmil at dcn.davis.ca.us> Basics: ##.#. ##.#. Live Go... Live: OO#.. Dead: OO#.. Playing Research Engineer (Solar/Batteries O.O#. #.O#. with /Software/Embedded Controllers) .OO#. .OO#. rocks...1k --------------------------------------------------------------------------- Sent from my phone. Please excuse my brevity. On May 14, 2014 7:51:36 AM PDT, carol white <wht_crl at yahoo.com> wrote:>Hi, >What is the elegant script to divide the columns of a matrix by the >respective position of a vector elements? > >m=rbind(c(6,4,2),c(3,2,1)) > >v= c(3,2,1) > >res= 6/3?? 4/2? 2/1 >??????? 3/3?? 2/2 ?? 1/1 > > >this is correct? >mat2 = NULL > >for (i in 1: ncol(m)) > >??? mat2 = cbind(mat2, m[,i]/ v[i]) > > >but how to do more compact and elegant with for ex do.call? > >Many thanks > >Carol > [[alternative HTML version deleted]] > > > >------------------------------------------------------------------------ > >______________________________________________ >R-help at 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.