If "monthly" should aggregate per "yyyy-mm" combination, you could try something like
aggregate(x$z,list(cut(as.Date(x$Date),"m")),mean) for monthly aggregation and aggregate(x$z,list(cut(as.Date(x$Date),"y")),mean) for yearly means. If monthly aggregation should aggregate over different years (and produce only 12 numbers), maybe aggregate(x$z, list(format(as.Date(x$Date),"%m")),mean) works (everything untested). Be sure to use R 2.4.1 patched or 2.5.0, since there was a bug in cut.Date which prevents the yearly aggregation from working properly before R 2.4.1 patched! Regards, Martin Michel Schnitz 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! > ______________________________________________ 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.
