Do you mean the mean for all January firsts, the mean for all January 2nds, etc.?
Look up ?format in addition to the commands you looked up before: tapply(DF$count, format(Dates, "%Y-%m"), mean) Terry Mu <muster <at> gmail.com> writes: : : Sorry, I didn't express my problem clearly. Your answers surely help, : but it's not what I meant to ask. : : I'd like mean for every day in a year, i.e, : mean for January 1st, 2nd, 3rd, .... : Febuary, 1st, ..., 28th, 29th(if leap year) : ... : : There is only one count per day, so there is no need to calculate mean : for each date. : : sorry for the confusion. I appreciate your further comment. : : Terry Mu : : : On Sun, 5 Dec 2004 12:04:26 -0500, Terry Mu <muster <at> gmail.com> wrote: : > thank you, : > : > one more question: : > : > How can I list only values for given condition? : > for example, I want to see only data from febuary, i.e. month=2? : > : > : > : > On Sun, 5 Dec 2004 16:26:11 +0000 (UTC), Gabor Grothendieck : > <ggrothendieck <at> myway.com> wrote: : > > Terry Mu <muster <at> gmail.com> writes: : > > : > > : : > > : a data set like this: : > > : > > : > > : : > > : year month day count : > > : 2001 1 1 10 : > > : 2001 1 2 11 : > > : .... : > > : 2004 7 17 8 : > > : .... : > > : : > > : basically it is a count of of some numbers everyday through a few years : > > : : > > : now I'd like to get the mean of the count for every day. : > > : : > > : I thought I can do this using for and ifelse, : > > : but is there a simple way to do this? I wish a function like : > > : mean(count, 'only when year, month, day are equal') could do this. : > > : > > You want to represent your dates as objects of the Date class : > > and then use tapply. (See ?as.Date, ?Date, ?tapply, ?paste, ?with. : > > Also look up ?aggregate and ?by and read about dates in R News 4/1.) : > > Assuming DF is your data frame: : > > : > > Dates <- with(DF, : > > as.Date( paste(year, month, day, sep="-") ) : > > ) : > > tapply(DF$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
