A character of same length as the number of points, or a single
logical TRUE or FALSE. If TRUE, an attempt is made to create labels
by pasting columns ID1 and ID2 in kappa, if these exist. By default,
no labels are plotted.
colLab, cexLab, pos, adj
Parameters passed onto text() (if labels is
non-NULL).
keep.par
A logical. If TRUE, the graphical parameters are not reset
after plotting, which may be useful for adding additional annotation.