HI, You can use either ?tapply(), ?aggregate(), ?ddply() from library(plyr) dat1<-read.table(text=" 0 12 1 10 1 4 1 6 1 7 1 13 2 21 2 23 2 20 3 18 3 17 3 16 3 27 3 33 4 11 4 8 4 19 4 16 4 9 ",sep="",header=FALSE) with(dat1,aggregate(dat1[,2],by=list(V1=dat1[,1]),sum)) # V1 x #1 0 12 #2 1 40 #3 2 64 #4 3 111 #5 4 63 A.K.
----- Original Message ----- From: T Bal <studentt...@gmail.com> To: r-help@r-project.org Cc: Sent: Tuesday, December 4, 2012 2:59 AM Subject: [R] question about sum of (column) elements in R Hi, I have the following data: 0 12 1 10 1 4 1 6 1 7 1 13 2 21 2 23 2 20 3 18 3 17 3 16 3 27 3 33 4 11 4 8 4 19 4 16 4 9 In this data file I would like to sum the numbers of second column which belong to the same number in the first column. So the output would be: 0 12 1 40 2 64 3 111 etc. Thank you. Kind regards, T. Bal [[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. ______________________________________________ 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.