Thank you for the suggestion. Tried it as : MeansByDoseDayTime <- aggregate(as.double(PK04Sub$Concentration.ng.mL.), by = list(PK04Sub$Dose.Level, PK04Sub$Day, PK04Sub$HourNominal), FUN = function(x) c( mean(x, trim = 0, na.rm = T, weights=NULL), sd(x, na.rm=TRUE), median(x, na.rm=TRUE), min(x, na.rm=TRUE), max(x, na.rm=TRUE) ) )
and got the following error message. Problem in FUN(...X.sub.i...., all.indices = c(1, 2..: FUN did not always return a scalar Suggestions? Regards, Michael -----Original Message----- From: David Winsemius [mailto:dwinsem...@comcast.net] Sent: Thursday, February 23, 2012 1:55 PM To: Michael Karol Cc: r-help@r-project.org Subject: Re: [R] Aggregate with Function List ? On Feb 23, 2012, at 1:41 PM, Michael Karol wrote: > R Experts > > > > I wish to tabulate into one data frame statistics summarizing > concentration data. The summary is to include mean, standard > deviation, median, min and max. I wish to have summaries by Dose, Day > and Time. I can do this by calling aggregate once for each of the > statistics (mean, standard deviation, median, min and max) and then > execute 4 merges to merging the 5 data frames into one. (Example > aggregate code for mean only is shown below.) > > Can someone show me the coding to do this as one command, rather than > 5 calls to aggregate and 4 merges. In other words, in essence, I'd > like to present to "FUN =" a list of functions, so all the summary > stats come back in one data frame. Your assistance is appreciated. > Thank you. > Perhaps something like this? MeansByDoseDayTime <- aggregate(as.double(DF$Concentration), by = list(DF$Dose, DF$Day, DF$Time), FUN = function(x) c( mean(x, trim = 0, na.rm = T, weights=NULL), sd(x, na.rm=TRUE), median(x, na.rm=TRUE), min(na.rm=TRUE), max(x, na.rm=TRUE) ) ) > > > 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.