Hi, I am trying to sum column information in a list with 3 instances.
For example: ID Traversed ID Traversed ID Traversed 1 5 1 7 1 8 2 8 2 11 2 7 3 11 3 22 3 16 What I want to do is sum the Traversed variable across all these instances so I can get a total value for Traversed for each ID column. So the end output should look like the following: ID Traversed 1 20 2 26 3 49 Basically, just sum up the columns by id. I am using the aggregate function, but it is not working. This is what I do: agW<-aggregate(rres,rres[c('ID')],sum) //rres is the list Error in FUN(X[[1L]], ...) : argument "INDEX" is missing, with no default //the error message I get As you can see, I get the index error when I try this above. Can anyone help? Thanks in advance. Mark ______________________________________________ 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.