it works. thanks a lot. Gabor Grothendieck wrote: > try this. The first group of lines recreates your data frame, DF, and > the last line is the aggregate: > > > Input <- "Date Time z > 2006-01-01 21:00 6,2 > 2006-01-01 22:00 5,7 > 2006-01-01 23:00 3,2 > 2006-01-02 00:00 7,8 > 2006-01-02 01:00 6,8 > 2006-01-02 02:00 5,6 > 2007-03-30 22:00 5,2 > 2007-03-30 23:00 8,3 > 2007-03-31 00:00 6,4 > 2007-03-31 01:00 7,4 > " > DF <- read.table(textConnection(Input), header = TRUE, as.is = TRUE) > DF$z <- as.numeric(sub(",", ".", DF$z)) > DF$Date <- as.Date(DF$Date) > > aggregate(DF["z"], list(yearmon = format(DF$Date, "%Y-%m")), mean) > > > > On 4/23/07, Michel Schnitz <[EMAIL PROTECTED]> wrote: > >> Hello, >> >> is there a way to use the aggregate function to calculate monthly mean >> in case i have one row in data frame that holds the date like >> yyyy-mm-dd? i know that it works for daily means. i also like to do it >> for monthly and yearly means. maybe there is something like aggregate(x, >> list(Date[%m]), mean)? >> the data frame looks like: >> >> Date Time z >> 2006-01-01 21:00 6,2 >> 2006-01-01 22:00 5,7 >> 2006-01-01 23:00 3,2 >> 2006-01-02 00:00 7,8 >> 2006-01-02 01:00 6,8 >> 2006-01-02 02:00 5,6 >> . >> . >> . >> 2007-03-30 22:00 5,2 >> 2007-03-30 23:00 8,3 >> 2007-03-31 00:00 6,4 >> 2007-03-31 01:00 7,4 >> >> thanks for help! >> -- >> Michél Schnitz >> [EMAIL PROTECTED] >> >> ______________________________________________ >> 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. >> >
-- Michél Schnitz [EMAIL PROTECTED] Scharrenstrasse 07 06108 Halle-Saale phone: +0049-(0)345- 290 85 24 mobile:+0049-(0)176- 239 000 64 ______________________________________________ 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.