thanks, this time it works perfectly. I use
tapply(DF$count, format(Dates, '%m-%d'), mean). as Patrick mentioned. It works without as.date(). with as.date() on, it gives a result one day after the actual date. I also got subset(). Thank you all very much. I like R and will learn more. Terry On Sun, 5 Dec 2004 17:33:23 +0000 (UTC), Gabor Grothendieck <[EMAIL PROTECTED]> wrote: > > Place Dates in DF and use subset(DF, month == 2) in place of DF. > I think you need to reread the Introduction to R manual since you > should find this sort of question answered there. If not the pointers > I gave you should get you started. > > Terry Mu <muster <at> gmail.com> writes: > > : > : thank you, > > > : > : one more question: > : > : How can I list only values for given condition? > : for example, I want to see only data from febuary, i.e. month=2? > : > : On Sun, 5 Dec 2004 16:26:11 +0000 (UTC), Gabor Grothendieck > : <ggrothendieck <at> myway.com> wrote: > : > Terry Mu <muster <at> gmail.com> writes: > : > > : > : > : > : a data set like this: > : > > : > > : > : > : > : year month day count > : > : 2001 1 1 10 > : > : 2001 1 2 11 > : > : .... > : > : 2004 7 17 8 > : > : .... > : > : > : > : basically it is a count of of some numbers everyday through a few years > : > : > : > : now I'd like to get the mean of the count for every day. > : > : > : > : I thought I can do this using for and ifelse, > : > : but is there a simple way to do this? I wish a function like > : > : mean(count, 'only when year, month, day are equal') could do this. > : > > : > You want to represent your dates as objects of the Date class > : > and then use tapply. (See ?as.Date, ?Date, ?tapply, ?paste, ?with. > : > Also look up ?aggregate and ?by and read about dates in R News 4/1.) > : > Assuming DF is your data frame: > : > > : > Dates <- with(DF, > : > as.Date( paste(year, month, day, sep="-") ) > : > ) > : > tapply(DF$count, Dates, mean) > : > > : > > : > > : > ______________________________________________ > : > R-help <at> 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 > : > > : > : ______________________________________________ > : R-help <at> 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 > : > : > > ______________________________________________ > > > [EMAIL PROTECTED] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html > ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html