[R] plot and factors

[Jason Miller]

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)?

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.)

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