R devel - Sep 2016 - R-intro: function 'stderr' and 'sd'

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))

>>>>> 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.)

While you are editing that, you might change its name from 'stderr'
to standardError (or standard_error, etc.) so as not to conflict with
base::stderr().


Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Tue, Sep 13, 2016 at 8:55 AM, Martin Maechler <maechler at
stat.math.ethz.ch
> wrote:
> >>>>> 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.)
>
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> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>
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