Hi, folks, I am sorry that I did not state the problem correctly yesterday.
Please let me address the problem by the following codes: first=c('u','b','e','k','j','c','u','f','c','e') second=c('usa','Brazil','England','Korea','Japan','China','usa','France','China','England') third=1:10 data=data.frame(first,second,third) ## You may understand values in the first column are the unique codes for those in the second column. ####So 'u' is only for usa. Replicate values appear the same rows for the first and second columns. ### Now I want to delete replicate rows with the same values in first (sceond) rows ####and sum up values in the third column for the same values. mm=melt(data,id='first') sum=cast(mm,first~variable,sum) ### This does not work. ###I tried another way to do this mm= melt(data, id='first',measure='third') sum=cast(mm,first~variable,sum) ## But then the problem is how to 'merge' the result with the second column in the dataset. The expected dataframe is like this: (I showed a wrong expected dataframe yesterday.) first second third 1 u usa 8 2 b Brazil 2 3 e England 13 4 k Korea 4 5 j Japan 5 6 c China 15 8 f France 8 Thanks in advance. [[alternative HTML version deleted]] ______________________________________________ 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.