You are somewhere in Circles 3 and 4 of 'The R Inferno'.
If you have a function to apply over more than one argument, then 'mapply' will do that. But you don't need to do that -- you can do the operation you want efficiently: *) create your resulting matrix with all zeros, no reason for this to be a data frame, almost surely. mainmat <- matrix(0, ncol=92, nrow=...) *) create a subscripting matrix giving the row and column combinations to change to 1. Here is a small example: > ss <- strsplit(c("1", "2,3", "1"), split=",") > sr <- rep(1:length(ss), sapply(ss, length)) > sr [1] 1 2 2 3 > sc <- as.numeric(unlist(ss)) > sc [1] 1 2 3 1 > mainmat[cbind(sr, sc)] <- 1 On 29/08/2011 14:55, Chris Beeley wrote:
Hello- Sorry to ask a basic question, but I've spent many hours on this now and seem to be missing something. I have a loop that looks like this: mainmat=data.frame(matrix(data=0, ncol=92, nrow=length(predata$Words_MH))) for(i in 1:length(predata$Words_MH)){ for(j in 1:92){ mainmat[i,j]=ifelse(j %in% as.numeric(unlist(strsplit(predata$Words_MH[i], split=","))), 1, 0) } } What it's doing is creating a matrix with 92 columns, that's the number of different codes, and then for every row of my data it looks to see if the code (code 1, code 2, etc.) is in the string and if it is, returns a 1 in the relevant column (column 1 for code 1, column 2 for code 2, etc.) There are 1000 rows in the database, and I have to run several versions of this code, so it just takes way too long, I have been trying to rewrite using lapply. I tried this: myfunction=function(x, y) ifelse(x %in% as.numeric(unlist(strsplit(predata$Words_MH[y], split=","))), 1, 0) for(j in 1:92){ mainmat[,j]= lapply(predata$Words, myfunction) } but I don't think I can use something that takes two inputs, and I can't seem to remove either. Here's a dput of the first 10 rows of the variable in case that's helpful: predata$Words=c("1", "1", "1", "1", "2,3,4", "5", "1", "1", "6", "7,8,9,10") Given these data, I want the function to return, for the first column, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0 (because those are the values of Words which contain a 1) and for the second column return 0, 0, 0, 0, 1, 0, 0, 0, 0, 0 (because the fifth value is the only one that contains a 2). Any suggestions gratefully received! Chris Beeley Institute of Mental Health, UK ______________________________________________ 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.
-- Patrick Burns pbu...@pburns.seanet.com twitter: @portfolioprobe http://www.portfolioprobe.com/blog http://www.burns-stat.com (home of 'Some hints for the R beginner' and 'The R Inferno') ______________________________________________ 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.