In "An Introduction to R" Version 3.3.1, in "4.2 The function tapply() and ragged arrays", after stderr <- function(x) sqrt(var(x)/length(x)) , there is a note in brackets: Writing functions will be considered later in [Writing your own functions], and in this case was unnecessary as R also has a builtin function sd().
The part "in this case was unnecessary as R also has a builtin function sd()" is misleading. The builtin function sd() doesn't calculate standard error of the mean. It calculates standard deviation. The function 'stderr' can use 'sd': function(x) sd(x)/sqrt(length(x)) ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
