[R] Storing output vector form a loop as a matrix Based on help files and searching the archives and help from the listserv I have managed to build my monte carlo program. However I cannot get the proper syntax for running the loop and storing the output of each loop (which is a vector) into a matrix. I took out some of the crazy code I was writing, but here is what I have: -------------------- rm(list = ls(all = TRUE)) # removes everything a <-c("A","C","B","A","B","C") b <-c(10,20,30,40,50,60) c <-data.frame(a,b) N=10 #Number of Loops output.matrix <- matrix(0.0,3,N) #I need to START LOOP HERE a <- sample(a, replace=TRUE) c <-data.frame(b,a) output.vector <- by(c, a, function(x) sum(x$b)) output.vector <- as.vector(output) output.vector <- data.frame(output) #END LOOP here -------------------------- What I would like to have at the end is the "output.matrix" contain as a column the  "output.vector" from  each iteration. The actual data frame I will be running has 60,000 observations and I am going to run 20000 iterations so speed is important too. Thanks so much EG 	[[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.