Dear all, I have 9 data frames, and I'm simply trying to sum the values of column 3 (on a row-by-row basis). However, there are a slightly different number of rows in each data frame, so I'm receiving the following error: "Error in Ops.data.frame(mrunoff_207101[3], mrunoff_207102[3]) : + only defined for equally-sized data frames".
Here is what I'm attempting to do: > arunoff_2071 <- cbind(mrunoff_207101[1:2], (mrunoff_207101[3] + > mrunoff_207102[3] + mrunoff_207103[3] + mrunoff_207104[3] + mrunoff_207105[3] > + mrunoff_207106[3] + mrunoff_207107[3] + mrunoff_207108[3] + > mrunoff_207109[3])) Is there an easy way of summing based on congruent values in columns 1 and 2? The only way I can think of would be to use merge, but this would involve doing this for every pair of data frames. The data for each data frame look like this: > head(mrunoff_207101) Latitude Longitude FPC 1 5.75 0.25 0.0112384744 2 6.25 0.25 0.0019959067 3 6.75 0.25 0.0003245941 4 7.25 0.25 0.0011973676 5 7.75 0.25 0.0001062602 6 8.25 0.25 0.0451578423 Any suggestions on how to achieve this easily will be very welcome. Many thanks, Steve ______________________________________________ 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.