Adai, Thank you so much for your help. I like your code the best. :) So simple. I have another question though, if you don't mind. I'd like to include another variable in "res". This variable defines the segmentation of each person (ranges, say, from 1 to 4). ID value Seg 111 5 2 111 6 2 111 2 2 178 7 4 178 3 4 138 3 1 138 8 1 138 7 1 138 6 1How to do this? Thank you so much for the help. Sincerely Julia
--- On Thu, 9/11/08, Adaikalavan Ramasamy <[EMAIL PROTECTED]> wrote: From: Adaikalavan Ramasamy <[EMAIL PROTECTED]> Subject: Re: [R] Calculate mean/var by ID To: "Jorge Ivan Velez" <[EMAIL PROTECTED]> Cc: "liujb" <[EMAIL PROTECTED]>, r-help@r-project.org Date: Thursday, September 11, 2008, 10:28 PM A slight variation of what Jorge has proposed is: f <- function(x) c( mu=mean(x), var=var(x) ) do.call( "rbind", tapply( df$value, df$ID, f ) ) mu var 111 4.333333 4.333333 138 6.000000 4.666667 178 5.000000 8.000000 Regards, Adai Jorge Ivan Velez wrote: > Dear Julia, > Try also > > x=read.table(textConnection("ID value > 111 5 > 111 6 > 111 2 > 178 7 > 178 3 > 138 3 > 138 8 > 138 7 > 138 6"),header=TRUE) > closeAllConnections() > attach(x) > > do.call(rbind,tapply(value,ID, function(x){ > res=c(mean(x,na.rm=TRUE),var(x,na.rm=TRUE)) > names(res)=c('Mean','Variance') > res > } > ) > ) > > HTH, > > Jorge > > > > > On Thu, Sep 11, 2008 at 1:45 PM, liujb <[EMAIL PROTECTED]> wrote: > >> Hello, >> >> I have a data set that looks like this. >> ID value >> 111 5 >> 111 6 >> 111 2 >> 178 7 >> 178 3 >> 138 3 >> 138 8 >> 138 7 >> 138 6 >> . >> . >> . >> >> I'd like to calculate the mean and var for each object identified by the >> ID. >> I can in theory just loop through the whole thing..., but is there a easier >> way/command which let me calculate the mean/var by ID? >> >> Thanks, >> Julia >> -- >> View this message in context: >> http://www.nabble.com/Calculate-mean-var-by-ID-tp19440461p19440461.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. >> > > [[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. [[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.