This generates a custom lattice boxplot; we super-impose
actual plot points for groups with a small number of
points, and also restrict plotting of the boxplot for
these as well (since they are really rather
mis-representative of the distribution when there are so
few points.) The downside is that functionality is not
implemented for multi-panel plots.
Usage
bwplot2(form, data = NULL, xlab = NULL, ylab = NULL,
main = NULL, n = 10, ...)