Whether 1, 2, or "all" d.f.s should be plotted. Note that for
scan.haplo.2D 1 and 2 d.f. list the same values.
Value
No value returned.
Details
Now plots only "allelelic" results. This is fine for scan.haplo.2Das only alleic tests are produced; however, scan.glm.2D also
produces "genotypic" results.