something like that should work : aggregate(test, list(test[,1]), mean)
2008/8/1 Bertolt Meyer <[EMAIL PROTECTED]> > Dear R users, > > I have a newbie-question that I couldn't resolve after reading through > several pieces of documentation and searching the archive. > > I have a data.frame containing experimental data from a group experiment in > psychology. Each line represents a single participant, but participants were > assigned to groups of three or four persons. One variable indicates each > participants' group number (groupID). For a large number of variables, I > would like to obtain the mean group value. I figured I use tapply() in the > fashion of tapply(variable, groupID, mean), but that would be a tiresome > task for my 150 variables. I am thus looking for a way to obtain a > data.frame that contains one row for each group with the group-mean > variables as columns. > > Example: > > > test <- as.data.frame(cbind(c(rep(1,5),rep(2,5)), rnorm(10), rnorm(10))) > > names(test)[1] <- "groupID" > > test > > groupID V2 V3 > 1 1 -0.82990860 -0.61778919 > 2 1 -0.01379452 0.64609053 > 3 1 -2.64990839 -1.00570627 > 4 1 -0.07903878 -0.70864441 > 5 1 0.61483071 -1.32039565 > 6 2 -0.18913937 1.38490710 > 7 2 -0.60017953 0.15893421 > 8 2 -0.99901931 0.05963436 > 9 2 -1.46759515 0.35040283 > 10 2 -0.44650422 -0.08713162 > > > tapply(test$V2, test$groupID, mean) > 1 2 > -0.5915639 -0.7404875 > > > tapply(test$V3, test$groupID, mean) > 1 2 > -0.6012890 0.3733494 > > I am now looking for something that gives me > > groupID V2 V3 > 1 1 -0.5915639 -0.6012890 > 2 2 -0.7404875 0.3733494 > > Any ideas? > > Thank you very much, > Bertolt > > -- > Bertolt Meyer > Oberassistent > Sozialpsychologie, Psychologisches Institut der Universität Zürich > Binzmühlestr. 14, Box 15 > CH-8050 Zürich > > [EMAIL PROTECTED] > tel: +41446357282 > fax: +41446357279 > mob: +41788966111 > > ______________________________________________ > 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. > [[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.
