I want to show over dispersion in my data by plotting the variance against
the mean for 8 groups.  I used the following code to plot by type
(parasite).

scatterplot(variance~mean | parasite, reg.line=lm, smooth=FALSE,
spread=FALSE, boxplots=FALSE, span=0.5, by.groups=TRUE, data=Disp2)

I now want to add a hypothetical regression line that would show what a 1:1
ratio would look on the same plot.

I also want to label specific points by their sample name, or by a specific
color.

help please?

-- 
Sagan C. Friant, MSc
Environment & Resources Ph.D Program
Nelson Institute of Environmental Studies
University of Wisconsin - Madison

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