[R] bwplot stats question

ripley@stats.ox.ac.uk ripley at stats.ox.ac.uk
Mon Feb 24 18:31:02 CET 2003

The documentation is

1) the code
2) ?boxplot
3) the standard references on EDA.  I'd have to look up which exactly, but 
my guess would be to look at

Velleman & Hoaglin (1981) ABC of EDA.
Hoaglin, Mosteller, Tukey (1983) Understanding Robust and Exploratory Data 

Some better references should be given on the help page.

On Mon, 24 Feb 2003, Ken Nussear wrote:

> Just wondering where the documentation exists for the statistics which 
> makeup the bwplot.
> I'm guessing that if R is like similar products that the graph is 
> constructed as
> The median is the filled circle. The box surrounding the filled circle 
> depicts the 25th and 75th quartile. The range of values is given by the 
> dotted lines (“whiskers”) outside of each box, and possible outliers 
> are given by the open circles outside the box.
> Is this close?

Yes.  They are I think hinges not quartiles (that's just a small 
difference in definition), and the whiskers extend to the most extreme 
data point less than 1.5*IQR outside the box.  Points beyond the whiskers 
eare plotted separately: they would be unusual for a Normal sample.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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