Hi, You could try: set.seed(24) dat1<- as.data.frame(matrix(sample(1:50,29*6,replace=TRUE),ncol=6))
((seq_len(nrow(dat1))-1)%/%6)+1 # [1] 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 4 4 4 4 4 4 5 5 5 5 5 #For a particular column: aggregate(dat1[,5],list(((seq_len(nrow(dat1))-1)%/%6)+1),FUN=mean) # Group.1 x #1 1 38.16667 #2 2 29.50000 #3 3 23.16667 #4 4 21.16667 #5 5 20.60000 #or for the whole columns aggregate(dat1,list(((seq_len(nrow(dat1))-1)%/%6)+1),FUN=mean) # Group.1 V1 V2 V3 V4 V5 V6 #1 1 28.33333 17.50000 12.66667 35.00000 38.16667 30.16667 #2 2 26.16667 31.33333 35.33333 19.66667 29.50000 24.83333 #3 3 24.00000 11.83333 20.00000 25.50000 23.16667 20.83333 #4 4 18.33333 23.33333 23.66667 20.33333 21.16667 21.16667 #5 5 22.60000 30.40000 17.40000 21.80000 20.60000 24.40000 #or library(plyr) res1<-ddply(dat1,.(((seq_len(nrow(dat1))-1)%/%6)+1),summarize,MeanV1=mean(V1)) colnames(res1)[1]<-"Group" res1 # Group MeanV1 #1 1 28.33333 #2 2 26.16667 #3 3 24.00000 #4 4 18.33333 #5 5 22.60000 A.K. ----- Original Message ----- From: jsf1982 <jamie.free...@ucl.ac.uk> To: r-help@r-project.org Cc: Sent: Tuesday, August 13, 2013 12:46 PM Subject: [R] Regular repeats Hi, Many apologies for the simplicity (hopefully!) of this request - I can't find it on the forum, but it may have been asked in the past. I have a data frame consisting of ~2000 rows. I simply want to take the average of the first 6, then the next 6, then the next 6 until the end of the table. The command mean(mole[1:6,c("PercentPI")]) gets me the first 6 rows (column is PercentPI), but I don't know how to increase the rows incrementally. Thanks in advance. J -- View this message in context: http://r.789695.n4.nabble.com/Regular-repeats-tp4673653.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.