Thank you Peter, yes this is what I need! John
----- Original Message ---- From: Peter Alspach <peter.alsp...@plantandfood.co.nz> To: array chip <arrayprof...@yahoo.com>; David Winsemius <dwinsem...@comcast.net> Cc: "r-help@r-project.org" <r-help@r-project.org> Sent: Thu, September 9, 2010 4:26:53 PM Subject: RE: [R] "sequeeze" a data frame Tena koe John ?aggregate maybe? HTH .... Peter Alspach > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r- > project.org] On Behalf Of array chip > Sent: Friday, 10 September 2010 11:13 a.m. > To: David Winsemius > Cc: r-help@r-project.org > Subject: Re: [R] "sequeeze" a data frame > > Thank you David. I probably didn't make my question clear enough. In > the end, I > want a "shorter" version of the original data frame, basically with > variable > "rep" removed, then just one row per id, time and mode combination. The > original > data frame has 54 rows, I wish to have a data frame with only 27 rows > after > average. > > Using ave() would produce the following 3 rows for example: > id time mode rep y avg.y > 1 1 0 R 1 -1.089540576 -0.21924078 > 19 1 0 R 2 -0.743374679 -0.21924078 > 37 1 0 R 3 1.175192908 -0.21924078 > > But I only need one row: > > id time mode avg.y > 1 1 0 R -0.21924078 > > Thanks again, > > John > > > > ----- Original Message ---- > From: David Winsemius <dwinsem...@comcast.net> > To: array chip <arrayprof...@yahoo.com> > Cc: r-help@r-project.org > Sent: Thu, September 9, 2010 3:21:15 PM > Subject: Re: [R] "sequeeze" a data frame > > > On Sep 9, 2010, at 5:47 PM, array chip wrote: > > > Hi, suppose I have a data frame as below: > > > >dat<- > cbind(expand.grid(id=c(1,2,3),time=c(0,3,6),mode=c('R','L'),rep=(1:3)), > y=rnorm(54)) > >) > > > > > > I kind of want to "squeeze" the data frame into a new one with > averaged "y" > >over > > "rep" for the same id, time and mode. taking average is easy with > tapply: > > > > tapply(dat$y, list(dat$id, dat$time, dat$mode), mean) > > Try: > > dat$avg.y <- ave(dat$y, dat$id, dat$time, dat$mode, FUN=mean) > > ?ave > > The syntax of ave is different than "tapply" or "by". The grouping > factors are > not presented as a list and the FUN argument comes after the ,..., so > it needs > to be named if different than the default of "mean". > > > > > But I want the result to be in the same format as "dat". Certainly, > we always > > can transform the result (array) into the data frame using a lot of > codes. But > > is there a simple way to do this? > > > > Thanks > > David Winsemius, MD > West Hartford, CT > > ______________________________________________ > 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. The contents of this e-mail are confidential and may be ...{{dropped:17}} ______________________________________________ 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.
