Hi: Here are three ways, but there are others:
# (1) # package doBy: library(doBy) summaryBy(value + value2 ~ class, data = df) class value.mean value2.mean 1 x 2.5 2.0 2 y 8.0 2.0 3 z 13.5 5.5 # (2) aggregate(): with(df, aggregate(list(val1 = value, val2 = value2), list(class), FUN = mean)) Group.1 val1 val2 1 x 2.5 2.0 2 y 8.0 2.0 3 z 13.5 5.5 # plyr solution library(plyr) ddply(df, .(class), summarise, val1 = mean(value), val2 = mean(value2)) class val1 val2 1 x 2.5 2.0 2 y 8.0 2.0 3 z 13.5 5.5 HTH, Dennis On Mon, Feb 22, 2010 at 1:13 AM, mirauta <bmira...@yahoo.com> wrote: > > Hello, > > Having the matrix d > > d > value value2 class > 1 1 1 x > 2 2 2 x > 3 3 3 x > 4 4 2 x > 5 5 1 y > 6 11 3 y > 7 12 4 z > 8 13 5 z > 9 14 6 z > 10 15 7 z > > I want to calculate the means and cov matrix for groups x,y,z. > I know how to do it the long way. > I tried to use tapply and kmeans but no good results. > (tapply is a good solution for only 1 variable) > > > Thank you > > Bogdan > > > -- > View this message in context: > http://n4.nabble.com/how-do-I-calculate-means-or-cov-matrix-for-multivariate-groups-tp1564157p1564157.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. > [[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.
