Boxplot across levels of a factor

-----Original Message-----
From: Prof Brian Ripley [mailto:ripley at stats.ox.ac.uk]
Sent: Tuesday, August 24, 2004 2:28 AM
To: Paul Boutros
Cc: R-Help
Subject: Re: [R] Boxplot across levels of a factor


On Tue, 24 Aug 2004, Paul Boutros wrote:

Hello,

I have a data-frame in which one-column is a factor:

str(data);

`data.frame':   194 obs. of  8 variables:
 $ Type         : Factor w/ 3 levels "Nuclear-Rec..",..: 1 2 2 

2 2 2 2 2 2 2

...
 $ Locus        : num  0.000571 0.004000 0.001429 0.004857 0.007429 ...

And I'd like to make a boxplot of the data$Locus values, where 

each level of

the factor gets its own box-and-whiskers plot.  I'm weak in R, 

but I thought

there might be some shortcut to automating this instead of just 

creating a

new data-structure with all the separate values?

There are two.  The simpler is

	boxplot(Locus ~ Type, data=data)

and you can also use

	with(data, boxplot(split(Locus, Type)))

(split() does automate the construction of a suitable data structure.)

-- 
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