Suharto Anggono Suharto Anggono via R-devel <r-devel at r-project.org>
on Fri, 9 Sep 2016 16:52:01 +0000 writes:
> 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))
You are right; thank you Suharto.
It now says
(Writing functions will be considered later in @ref{Writing your own
functions}. Note that @R{}'s a builtin function @code{sd()} is something
different.)