michael watson (IAH-C) wrote: > > Check out rowMeans to average over replicate columns first, ie: > > means <- data.frame(t1=rowMeans(a[,1:3]), > t2=rowMeans(a[,4:6]), > etc) > > Then, if you want to aggregate every 14 rows: > > aggregate(means, by=list(rows=rep(1:(nrow(means)/14), each=14)), mean) > > Or something... > > YES! This seems to work. Thank you! > > -----Original Message----- > From: [EMAIL PROTECTED] on behalf of Silvia Lomascolo > Sent: Thu 07/06/2007 8:26 PM > To: r-help@stat.math.ethz.ch > Subject: [R] Averaging across rows & columns > > > I use Windows, R version 2.4.1. > > I have a dataset in which columns 1-3 are replicates, 4-6, are replicates, > etc. I need to calculate an average for every set of replicates (columns > 1-3, 4-6, 7-9, etc.) AND each set of replicates should be averaged every > 14 > rows (for more detail, to measure fruit color using a spectrometer, I > recorded three readings per fruit -replicates- that I need to average to > get > one reading per fruit; each row is a point in the light spectrum and I > need > to calculate an average reading every 5nm -14 rows- for each fruit). > > Someone proposed to another user who wanted an avg across columns to do > > a <- matrix(rnorm(360),nr=10) > b <- rep(1:12,each=3) > avgmat <- aggregate(a,by=list(b)) > > I tried doing this to get started with the columns first but it asks for > an > argument FUN that has no default. The help for aggregate isn't helping me > much (a new R user) to discover what value to give to FUN -'average' > doesn't > seem to exist, and 'sum' (whatever it is supposed to sum) gives an error > saying that arguments should have the same length- > > Any help will be much appreciated! > Silvia. > -- > View this message in context: > http://www.nabble.com/Averaging-across-rows---columns-tf3885900.html#a11014649 > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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. > > -- View this message in context: http://www.nabble.com/Averaging-across-rows---columns-tf3885900.html#a11015925 Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@stat.math.ethz.ch 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.