Hi, Your mistake seems to be in
sum(v[1:x]) You create "x" as a vector but your treat it as a single number. v[1:x] expects "x" to be a single number and only considers its first element which is 1. If I understand your query correctly, the following might handle your problem: sum.vec <-NULL for (x in 1:1000){ t <- rbinom(1000, 1, 0.5) v <- replace(t,t==0,-1) sum.vec<-c(sum.vec,sum(v[1:x])) } Best Ozgur ----- ************************************ Ozgur ASAR Research Assistant Middle East Technical University Department of Statistics 06531, Ankara Turkey Ph: 90-312-2105309 http://www.stat.metu.edu.tr/people/assistants/ozgur/ -- View this message in context: http://r.789695.n4.nabble.com/Warning-message-numerical-expression-has-1000-elements-only-the-first-used-tp4631813p4631903.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.