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R-intro: function 'stderr' and 'sd'

4 messages · Suharto Anggono Suharto Anggono, William Dunlap, Martin Maechler

Original
Suharto Anggono Suharto Anggono
# 
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))
3 days later
Martin Maechler
# 
> 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.)
William Dunlap
# 
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

  
  


  


      

    

    

      
      

        


  

        

      Martin Maechler
    

    

      
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> 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().

oh yes.. blush! ..
Martin

    > 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
    >> 

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