How about: y <- c(1,1,1,3,2) m <- matrix(0, nrow=length(y), ncol=4) m[y==1, ] <- matrix(1:4, nrow=sum(y == 1), ncol=4, byrow=TRUE)
or, depending on your actual problem y <- c(1,1,1,3,2) m <- matrix(0, nrow=length(y), ncol=4) m[y == 1,] <- col(m[y == 1,]) Sarah On Mon, Jun 20, 2011 at 3:54 PM, Costis Ghionnis <conigh...@gmail.com> wrote: > Hallo everyone! I have a problem about creating a matrix... > > Suppose we have a vector y<-c(1,1,1,3,2) > > and a zero matrix, m ,with nrows=length(y) and ncol=4. > > The matrix would look like this: > 0 0 0 0 > 0 0 0 0 > 0 0 0 0 > 0 0 0 0 > 0 0 0 0 > > I want to change the first three rows with the vector c(1,2,3,4). > I thought that with the command m[y==1,1:4]<-c(1,2,3,4) i would get > > 1 2 3 4 > 1 2 3 4 > 1 2 3 4 > 0 0 0 0 > 0 0 0 0 > > but instead i am getting > > 1 4 3 2 > 2 1 4 3 > 3 2 1 4 > 0 0 0 0 > 0 0 0 0 > > It seems it is filling the data by col instead by row. I want to use this > technique in more complicated problems. > So i do not want to have to work with the transpose matrix. Do you know > another way to make this work. Thank you... > -- Sarah Goslee http://www.functionaldiversity.org ______________________________________________ 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.
