[R] plot and factors

Petr Pikal petr.pikal at precheza.cz
Fri Dec 2 14:11:02 CET 2005


On 2 Dec 2005 at 6:40, Jason Miller wrote:

To:             	r-help at stat.math.ethz.ch
From:           	Jason Miller <millerj at truman.edu>
Date sent:      	Fri, 2 Dec 2005 06:40:48 -0600
Subject:        	[R] plot and factors

> Read R-helpers,
> I'm relatively new to R and trying to jump in feet first.  I've been 
> able to learn a lot from on-line and printed documentation, but 
> here's one question to which I can't find an answer.  Well, it's a 
> question with a couple parts.  Thanks in advance for any direction 
> (partial or complete) that anyone can provide.
> I have a data frame with three columns: Year, Semester, value1.  I 
> want to treat Year and Semester as factors; there are many years, and 
> there are three semesters (Fall, Spring, Summer).
> First, I would like to be able to plot the data in this frame as Year 
> v. value with one curve for each factor.  I have been unable to do 
> this.  Is there any built-in R functionality that makes this easy, or 
> do I need to build this by hand (e.g., using the techniques in FAQ 
> 5.11 or 5.29)?

Not sure what do you want to achieve. If x is factor you will get 
boxplots by

plot(factor, data)

so maybe stayinng with numeric and labeling with

plot(year,data, axes=FALSE)
axis(1, ....)

can be what you want.

> Second, I would like to be able to plot the values against a doubly 
> labeled axis that uses Year and Semester (three Semester ticks per 
> Year).  Is there a relatively straightforward way to do this?  
> (What's happening, of course, is that I'd like to treat Year+Semester 
> as a single factor for the purpose of marking the axis, but I'm not 
> sure how to do that, either.)

Try to look at ?interaction, maybe this can help you.


> Again, thanks for whatever pointers people can share.
> Jason
> ================================================================
> Jason E. Miller, Ph.D.
> Associate Professor of Mathematics
> Truman State University
> Kirksville, MO
> http://pyrite.truman.edu/~millerj/
> 660.785.7430
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Petr Pikal
petr.pikal at precheza.cz

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