[R] GWA plot

[kk473 at columbia.edu]

I need some help with a genome-wide association scatterplot. A  
recently published example of such a plot is attached to this message.

Typical variables include:
Y: -logP-value (range from 0 to 8)
X: chromosomal distance
Z: chromosomes 1 through 22 and X (a factor with 23 levels)

I used coplot(Y~X|CHR) and xyplot(Y~X|CHR), but I am not sure how to  
get the entire graph in a single panel (see attached). Please let me  
know if there is any simple way to produce such a plot using the  
existing R graphing commands.

Thanks!

Chris