[R] understanding patterns in categorical vs. continuous data

[Dylan Beaudette]

Greetings,

I have a set of bivariate data: one variable (vegetation type) which is 
categorical, and one (computed annual insolation) which is continuous. 
Plotting veg_type ~ insolation produces a nice overview of the patterns that 
I can see in the source data. However, due to the large number of samples 
(1,000), and the apparent "spread" in the distribution of a single vegetation 
type over a range of insolation values- I having a hard time quantitatively 
describing the relationship between the two variables. 

Here is a link to a sample graph:
http://casoilresource.lawr.ucdavis.edu/drupal/node/162

Since the data along each vegetation type "line" is not a distribution in the 
traditional sense, I am having problems applying descriptive statistical 
methods. Conceptually, I would like to some how describe the variation with 
insolation, along each vegetation type "line".

Any guidance, or suggested reading material would be greatly appreciated.


-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341