Re: [R] Assignment from list try the following: z <- matrix(1, ncol = 249, nrow = 240) zz <- matrix(1, ncol = 249, nrow = 240) for (k in seq_along(x)) {     z[rbind(x[[k]])] <- 0 } zz[xx] <- 0 all.equal(z, zz) I hope it helps. Best, Dimitris ---- Dimitris Rizopoulos Ph.D. Student Biostatistical Centre School of Public Health Catholic University of Leuven Address: Kapucijnenvoer 35, Leuven, Belgium Tel: +32/(0)16/336899 Fax: +32/(0)16/337015 Web: http://med.kuleuven.be/biostat/      http://www.student.kuleuven.be/~m0390867/dimitris.htm ----- Original Message -----  From: "Eric Blanc"  To:  Sent: Thursday, April 12, 2007 10:36 AM Subject: [R] Assignment from list >I have a list of groups of xy positions I want to set to 0 in an > array full of 1s. When the assignments are done directly from the > list, they are incorrect, while if I use a temporary array derived > from the list the assignments are correct. The following example  > will > hopefully make my problem clearer. > > The matrices z and zz are initialised with 1. The z and zz values at > coordinates in list x are then set to 0 using two different methods. > Although either method should lead to the same results, z and zz are > different. z is incorrect, because some values in its first row have > been incorrectly set to 0. > > x  <- list( matrix( c( 9, 9, 74, 75 ), nrow=2 ), >             matrix( c( 11, 11, 34, 35 ), nrow=2 ), >             matrix( c( 14, 15, 58, 58 ), nrow=2 ), >             c( 16, 142 ), >             matrix( c( 19, 19, 94, 95 ), nrow=2 ), >             matrix( c( 19, 20, 127, 127 ), nrow=2 ), >             matrix( c( 22, 22, 112, 113 ), nrow=2 ), >             c( 23, 13 ), >             matrix( c( 26, 27, 81, 81 ), nrow=2 ), >             matrix( c( 31, 32, 153, 153 ), nrow=2 ) ) > xx <- do.call( "rbind", x ) > > z <- matrix( 1, ncol=249, nrow=240 ) > zz <- matrix( 1, ncol=249, nrow=240 ) > > for( k in x ) z[k] <- 0 > zz[xx] <- 0 > > sum( z != zz ) > c( sum( z[,1] != 1 ), sum( zz[,1] != 1 ) ) > > Somewhere, I must be doing something wrong, or assuming something > incorrect. I would be very grateful if anybody could point me in the > right direction. > > platform       i386-apple-darwin8.8.1 > arch           i386 > os             darwin8.8.1 > system         i386, darwin8.8.1 > status > major          2 > minor          4.1 > year           2006 > month          12 > day            18 > svn rev        40228 > language       R > version.string R version 2.4.1 (2006-12-18) > > (same results with platform i386-pc-mingw32, R version 2.4.1 and > platform x86_64-unknown-linux-gnu, R version 2.3.1) > > -- > Dr Eric Blanc > Lecturer in Bioinformatics > MRC Centre for Developmental Neurobiology > King's College London > New Hunt's House Room 4.10B > Guy's Hospital Campus > London SE1 1UL > > E-mail: eric.blanc@kcl.ac.uk > Tel: +44 (0)20 7848 6532 > Fax: +44 (0)20 7848 6550 > > > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@stat.math.ethz.ch 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. >  Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm ______________________________________________ R-help@stat.math.ethz.ch 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.