[R] boxplot statistics

[Liaw, Andy]

> From: Graham Williams
> 
> Received Tue 04 Oct 2005  7:26pm +1000 from Karin Lagesen:
> > 
> > I have read and reread the boxplot and the boxplot stats page, and I
> > still cannot understand how and what boxplot shows. I realize that
> > this might be due to me not knowing enough statistics, but anyway...
> > 
> > First, how does boxplot determine the size of the box? And 
> is the line
> > inside the box the mean or the median (or something completely
> > different?) And how does it determine how long out the 
> whiskers should
> > go?
> > 
> > Also, the boxplot.stats page talks about "hinges", what are those?  
> > "The two "hinges" are versions of the first and third 
> quartile, i.e.,
> > close to 'quantile(x, c(1,3)/4)'."
> 
> Wikipedia has a reasonable description
> 
>	   http://en.wikipedia.org/wiki/Boxplot

... but not quite accurate.  If I'm not mistaken, boxplots are based on
Tukey's letter values.  Here's one description of what they are:

http://www.math.yorku.ca/SCS/Courses/eda/eda1.html#H2_32:1.2

Andy