On Thu, 4 Aug 2005, Matt Crawford wrote: > I understand that in R, for loops are not used as often as other > languages, and am trying to learn how to avoid them. I am wondering > if there is a more efficient way to write a certain piece of code, > which right now I can only envision as a for loop. I have a data file > that basically looks like: > 1,55 > 1,23 > 2,12 > ... > that defines a matrix. Each row of the data file corresponds to a row > of the matrix, where each number in the row tells me what column a "1" > or "-1" should go into. So the first row in the data snippet above > means that the first row of my matrix needs to have a 1 in the 1st > column, and a -1 in the 55nd column. (And 0 elsewhere, which is > already there as I've created the matrix filled with 0s beforehand.) >
This may be a job for matrix indexes ii<-1:nrow(rawdata) X[cbind(ii,rawdata[,1])] <- 1 X[cbind(ii,rawdata[,2])] <- -1 -thomas ______________________________________________ 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