Why do you want to do this? X[,"cname"] gives the column named "cname" of matrix X (as a vector, unless drop=FALSE). The $ operator on data frames is essentially equivalent to this, anyway (see ? Extract).
-- Bert Gunter Genentech -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dan Dube Sent: Friday, January 04, 2008 11:29 AM To: r-help@r-project.org Subject: [R] slow access to matrix dimnames hello, i have been trying to convert my data frames to matrices in the hopes of speeding up some of my more complicated scripts. to assist with this, i am trying to create a "matrix column operator" like $: "%$%" = function(data,field) { as.numeric(data[,grep(field,unlist(dimnames(data)[2]))]) } the idea here is that you can use a matrix like a dataframe: matrix%$%"fieldname" i am getting this matrix by converting a dataframe: df = read.csv("data.csv") matrix = data.matrix(df,rownames.force=FALSE) this sets rownames to "NULL", but there is still an entry at dimnames(matrix)[1], and so i have to access the actual column names as dimnames(matrix)[2]. if there were only one dimension of dimnames, this operator works quickly, but when i have to access [2], it is super slow. am i way off base trying to do this? i'd like to have the ability to talk about the columns by name, since they may not always be in the same place. maybe i am making it more complicated than necessary? thanks! dan ______________________________________________ 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.