[R] creating bins for a plot

[Jeffrey Stratford]

Hi.  I'm trying to plot the ratio of used versus unused bird houses
(coded 1 or 0) versus a continuous environmental gradient (proportion of
 urban cover [purban2]) that I would like to convert into bins (0 -
0.25, 0.26 - 0.5, 0.51 - 0.75, 0.76 - 1.0) and I'm not having much luck
figuring this out.  I ran a logistic regression and purban2 ends up
driving the probability of a box being occupied so it would be nice to
show this relationship.  I'm also plotting the fitted values vs. purban2
but that's done.  Any suggestions would be appreciated.

Many thanks,

Jeff


Data sample:

box	use	purbank	purban2
1	1	0.003813435	0.02684564
2	1	0.04429451	0.1610738
3	1	0.04458785	0.06040268
4	1	0.06072162	0.2080537
5	0	0.6080962	0.6979866
6	1	0.6060428	0.6107383
7	1	0.3807568	0.4362416
8	0	0.3649164	0.3154362
9	0	0.3505427	0.2483221
10	0	0.3476093	0.1409396
11	0	0.3719566	0.3020134
12	1	0.09238011	0.1342282
13	0	0.08616111	0.1073826
14	0	0.07388724	0.04026845
15	1	0.07046477	0.03355705
.
.
.


****************************************
Jeffrey A. Stratford, Ph.D.
Postdoctoral Associate
331 Funchess Hall
Department of Biological Sciences
Auburn University
Auburn, AL 36849
334-329-9198
FAX 334-844-9234
http://www.auburn.edu/~stratja