Suharto Anggono Suharto Anggono
2016-Sep-09 16:52 UTC
[Rd] 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.) > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel >[[alternative HTML version deleted]]