Dear list, Please find below an example of odd behaviour of the by function.
It occurs both under GNU/Linux R 2.6.2 and Windows R 2.7.0alpha. Respective sessionInfo()'s are given below. I hope I do not overlook anything. testFactor <- factor(sample(LETTERS[1:6], size = 42, replace = TRUE)) testMatrix <- matrix(rnorm(42 * 6), nrow = 42) testDf <- as.data.frame(testMatrix) by(data = testDf, INDICES = testFactor, FUN = mean) # OK by(data = testDf, INDICES = testFactor, FUN = median) # error # Error in median.default(data[x, ], ...) : need numeric data Kind regards, Tobias ### GNU/Linux ### > sessionInfo() R version 2.6.2 (2008-02-08) i486-pc-linux-gnu locale: LC_CTYPE=en_US.UTF-8;LC_NUMERIC=C;LC_TIME=en_US.UTF-8;LC_COLLATE=en_US.UTF-8;LC_MONETARY=en_US.UTF-8;LC_MESSAGES=en_US.UTF-8;LC_PAPER=en_US.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US.UTF-8;LC_IDENTIFICATION=C attached base packages: [1] tools stats graphics grDevices utils datasets methods [8] base other attached packages: [1] Biobase_1.16.3 ### Windows ### > sessionInfo() R version 2.7.0 alpha (2008-03-29 r44988) i386-pc-mingw32 locale: LC_COLLATE=English_United Kingdom.1252;LC_CTYPE=English_United Kingdom.1252;LC_MONETARY=English_United Kingdom.1252;LC_NUMERIC=C;LC_TIME=English_United Kingdom.1252 attached base packages: [1] stats graphics grDevices utils datasets methods base > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel