[Rd] R-intro: function 'stderr' and 'sd'

Suharto Anggono Suharto Anggono suharto_anggono at yahoo.com
Fri Sep 9 18:52:01 CEST 2016


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))



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