Dear all, Thanks for the contributions so far. I've had a look at these and the closest I've come to solving it is the following:
> data_ave <- ave(data$rammday, by=c(data$month, data$year)) Warning messages: 1: In split.default(x, g) : data length is not a multiple of split variable 2: In split.default(seq_along(x), f, drop = drop, ...) : data length is not a multiple of split variable I'm slightly confused by the warning message, as the data lengths do appear the same: > dim(data) [1] 1073 6 > length(data$year) [1] 1073 > length(data$month) [1] 1073 Maybe the approach I'm taking is wrong. Any suggestions would be gratefully received. Many thanks, Steve ---------------------------------------- > Date: Wed, 31 Mar 2010 23:31:25 +0200 > From: stephan.kola...@gmx.de > To: smurray...@hotmail.com > CC: r-help@r-project.org > Subject: Re: [R] Summing data based on certain conditions > > ?by may also be helpful. > > Stephan > > > Steve Murray schrieb: >> Dear all, >> >> I have a dataset of 1073 rows, the first 15 which look as follows: >> >>> data[1:15,] >> date year month day rammday thmmday >> 1 3/8/1988 1988 3 8 1.43 0.94 >> 2 3/15/1988 1988 3 15 2.86 0.66 >> 3 3/22/1988 1988 3 22 5.06 3.43 >> 4 3/29/1988 1988 3 29 18.76 10.93 >> 5 4/5/1988 1988 4 5 4.49 2.70 >> 6 4/12/1988 1988 4 12 8.57 4.59 >> 7 4/16/1988 1988 4 16 31.18 22.18 >> 8 4/19/1988 1988 4 19 19.67 12.33 >> 9 4/26/1988 1988 4 26 3.14 1.79 >> 10 5/3/1988 1988 5 3 11.51 6.33 >> 11 5/10/1988 1988 5 10 5.64 2.89 >> 12 5/17/1988 1988 5 17 37.46 20.89 >> 13 5/24/1988 1988 5 24 9.86 9.81 >> 14 5/31/1988 1988 5 31 13.00 8.63 >> 15 6/7/1988 1988 6 7 0.43 0.00 >> >> >> I am looking for a way by which I can create monthly totals of rammday >> (rainfall in mm/day; column 5) by doing the following: >> >> For each case where the month value and the year are the same (e.g. 3 and >> 1988, in the first four rows), find the mean of the the corresponding >> rammday values and then times by the number of days in that month (i.e. 31 >> in this case). >> >> Note however that the number of month values in each case isn't always the >> same (e.g. in this subset of data, there are 4 values for month 3, 5 for >> month 4 and 5 for month 5). Also the months will of course recycle for the >> following years, so it's not simply a case of finding a monthly total for >> *all* the 3s in the whole dataset, just those associated with each year in >> turn. >> >> How would I go about doing this in R? >> >> Any help will be gratefully received. >> >> Many thanks, >> >> Steve >> >> >> >> _________________________________________________________________ >> We want to hear all your funny, exciting and crazy Hotmail stories. Tell us >> now >> >> ______________________________________________ >> R-help@r-project.org 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. >> > _________________________________________________________________ Do you have a story that started on Hotmail? Tell us now ______________________________________________ R-help@r-project.org 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.
