Sure: df.count.mon$time<-format(as.Date(paste(df.count.mon$year, df.count.mon$mon,1), '%Y %m %d'),"%Y %m") > df.count.mon count year mon time 1 22 2014 1 2014 01 2 12 2014 2 2014 02 ...
Jim On Thu, Feb 23, 2017 at 8:18 AM, lily li <chocol...@gmail.com> wrote: > Yes, it is a little different. Is there a way to get 'yyyy-mm' format? > Thanks. > > On Wed, Feb 22, 2017 at 2:10 PM, Jim Lemon <drjimle...@gmail.com> wrote: >> >> Hi Lily. >> Two problems. You have named the month field "mon" and then refer to >> it as "month". Second, as the resolution of as.Date is days, it can't >> produce a valid date without specifying the day. Thus: >> >> df.count.mon<-data.frame(count=sample(1:24,24), >> year=rep(2014:2015,each=2),mon=rep(1:12,2)) >> # make each day the first day of the month >> df.count.mon$time<- >> as.Date(paste(df.count.mon$year, df.count.mon$mon,1), >> '%Y %m %d') >> df.count.mon >> count year mon time >> 1 22 2014 1 2014-01-01 >> 2 12 2014 2 2014-02-01 >> ... >> You will get values, but I don't think they are the ones you want. >> >> Jim >> >> On Thu, Feb 23, 2017 at 6:33 AM, lily li <chocol...@gmail.com> wrote: >> > Hi R users, >> > >> > I have a dataframe, with year, month, day, and other variables. I wanted >> > to >> > calculated monthly values of the variables. For example, there is one >> > variable called 'count'. I use the code below to convert daily data to >> > monthly data. >> > >> > df.count.mon = aggregate(count ~ year+month, data= df, sum) >> > >> > The new dataframe has three columns: year, month, and count. Now I want >> > to >> > add one more column as 'time', which has the format 'yyyy-mm'. I use the >> > code below but the new column has all NA values. What is the problem and >> > how to solve it? >> > >> > df.count.mon$time = as.Date(paste(df.count.mon$year, >> > df.count.mon$month), >> > '%Y %m') >> > >> > I had experience to add one more column with the format 'yyyy-mm-dd', >> > which >> > works, but not with monthly format. Thanks for your help. >> > >> > [[alternative HTML version deleted]] >> > >> > ______________________________________________ >> > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >> > 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. > > ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
