Not sure why you think tapply is "awkward". Your example would be...
group <- rep(1:5, each=5) variable <- rnorm(25) tapply(variable, group, max) ...which looks quite elegant to me :) Meanwhile, the reason your expression doesn't work is that you are asking mistakenly for elements 1:5 repeatedly from the variable col. If you just type d$variable[ d$group ] and compare the values to your variable vector this should be clear. Michael On 21 September 2010 10:59, Seth W Bigelow <sbige...@fs.fed.us> wrote: > I'm writing an expression that requires searching a vector according to > group. As an example, I want to find the maximum value in each of 5 > groups. > > > group=rep(1:5, each=5) # create grouping variable > > variable=rnorm(25) # generate data > > d <- data.frame(group,variable) # make data frame > > max(d$variable[d$group]) # try expression that > doesn't work > > I'm expecting a vector containing the maximum variable value, per group. > What am I doing wrong? I know I can use aggregate, tapply, etc. but that > seems awkward and bulky, is there a simpler way? > > > Dr. Seth W. Bigelow > Biologist, USDA-FS Pacific Southwest Research Station > 1731 Research Park Drive, Davis California > > [[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. > ______________________________________________ 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.
