Hi, Maybe something like this (inspired by ?cut),
cut2num <- function(f){ labs <- levels(f) d <- data.frame(lower = as.numeric( sub("\\((.+),.*", "\\1", labs) ), upper = as.numeric( sub("[^,]*,([^]]*)\\]", "\\1", labs) )) d$midpoints <- rowMeans(d) d } a <- c(1, 2, 3, 4, 5, 2, 3, 4, 5, 6, 7) cut2num(cut(a, 3)) HTH, baptiste 2009/11/8 jose romero <jlauren...@yahoo.com>: > Hello list: > > I am using "cut" and "table" to obtain a frequency table from a numeric > sample vector. The idea is to calculate mean and standard deviation on > grouped data. However, I can't extract the midpoints of the class intervals, > which seem to be strings treated as factors. How do i extract the midpoint? > > Thanks, > jose loreto > > > [[alternative HTML version deleted]] > > > ______________________________________________ > 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. > > ______________________________________________ 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.