[R] plot and factors

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

```Hi

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.

HTH
Petr

>
> 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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