Dear List, I'm not even sure this is an issue or not, but ?rowMeans has:
Value: A numeric or complex array of suitable size, or a vector if the result is one-dimensional. The ‘dimnames’ (or ‘names’ for a vector result) are taken from the original array. If there are no values in a range to be summed over (after removing missing values with ‘na.rm = TRUE’), that component of the output is set to ‘0’ (‘*Sums’) or ‘NA’ (‘*Means’), consistent with ‘sum’ and ‘mean’. However the output of mean() and rowMeans() is not exactly the same when all supplied values are missing. > mean(NA, na.rm = TRUE) [1] NaN > mean(rep(NA, 5), na.rm = TRUE) [1] NaN > rowMeans(matrix(rep(NA, 5), ncol = 5), na.rm = TRUE) [1] NA So in one sense, the outputs are not consistent: > is.nan(mean(rep(NA, 5), na.rm = TRUE)) [1] TRUE > is.nan(rowMeans(matrix(rep(NA, 5), ncol = 5), na.rm = TRUE)) [1] FALSE but in another they are: > is.na(mean(rep(NA, 5), na.rm = TRUE)) [1] TRUE > is.na(rowMeans(matrix(rep(NA, 5), ncol = 5), na.rm = TRUE)) [1] TRUE I'm not familiar enough with the details to know if this even matters, but wonder if something in the documentation needs a change or tweak to clarify what is returned. As I say, in one sense the outputs are not consistent. > sessionInfo() R version 2.13.0 beta (2011-04-04 r55298) Platform: x86_64-unknown-linux-gnu (64-bit) locale: [1] LC_CTYPE=en_GB.utf8 LC_NUMERIC=C [3] LC_TIME=en_GB.utf8 LC_COLLATE=en_GB.utf8 [5] LC_MONETARY=C LC_MESSAGES=en_GB.utf8 [7] LC_PAPER=en_GB.utf8 LC_NAME=C [9] LC_ADDRESS=C LC_TELEPHONE=C [11] LC_MEASUREMENT=en_GB.utf8 LC_IDENTIFICATION=C attached base packages: [1] stats graphics grDevices utils datasets methods [7] base loaded via a namespace (and not attached): [1] tools_2.13.0 Thanks, Gavin -- %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% Dr. Gavin Simpson [t] +44 (0)20 7679 0522 ECRC, UCL Geography, [f] +44 (0)20 7679 0565 Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/ UK. WC1E 6BT. [w] http://www.freshwaters.org.uk %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel