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 <[EMAIL PROTECTED]> 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) > > > > ______________________________________________ > [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
