Does the following do what you want? > i <- cbind(seq_len(nrow(x)), x[,4]) > x[i] [1] 11 23 32 > x[i] <- x[i] + 5 > x [,1] [,2] [,3] [,4] [1,] 16 12 13 1 [2,] 21 22 28 3 [3,] 31 37 33 2
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 Joris Meys > Sent: Friday, June 18, 2010 5:08 PM > To: Iuri Gavronski > Cc: r-help > Subject: Re: [R] Non-procedural access to columns of a matrix > > > diag(x[,x[,4]]) > [1] 11 23 32 > > > diag(x[,x[,4]]) <- diag(x[,x[,4]])+5 > > x > [,1] [,2] [,3] [,4] > [1,] 16 12 13 1 > [2,] 21 22 28 3 > [3,] 31 37 33 2 > > Cheers > Joris > > On Fri, Jun 18, 2010 at 8:58 PM, Iuri Gavronski <i...@ufrgs.br> wrote: > > Hi, > > > > I would like to have an index for a column in a matrix encoded in a > > cell of the same matrix. > > For example: > > x = matrix(c(11,12,13,1, > > 21,22,23,3, > > 31,32,33,2),byrow=T,ncol=4) > > > > In this case, column 4 is the index. I then access the column > > specified in the index by: > >> for (i in 1:3) print(x[i,x[i,4]]) > > [1] 11 > > [1] 23 > > [1] 32 > >> > >> for (i in 1:3) {x[i,x[i,4]] <- x[i,x[i,4]] + 5} > >> x > > [,1] [,2] [,3] [,4] > > [1,] 16 12 13 1 > > [2,] 21 22 28 3 > > [3,] 31 37 33 2 > >> > > > > Is there a way to get the same results without looping? > > > > Best, > > > > Iuri. > > > > ______________________________________________ > > 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. > > > > > > -- > Joris Meys > Statistical consultant > > Ghent University > Faculty of Bioscience Engineering > Department of Applied mathematics, biometrics and process control > > tel : +32 9 264 59 87 > joris.m...@ugent.be > ------------------------------- > Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php > > ______________________________________________ > 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.