Plots the genetic map for each chromosome, or a comparison of the
genetic maps if two maps are given.
For a comparison of two maps, the first
map is on the left (or, if horizontal=TRUE
, on the top). Lines
are drawn to connect markers. Markers that exist in just one map and
not the other are indicated by short line segments, on one side or the
other, that are not connected across.
For a sex-specific map, female and male maps are plotted against one
another. For two sex-specific maps, the two female maps are plotted
against one another and the two male maps are plotted against one
another.