An optional argument to attempt to separate variable names into
landmark dimension
and landmark number variables. For example, X.1, Y.1, Z.1, X.2, Y.2, Z.2,
..., can be separated
with sep = ".", such that rows of landmark configurations are labeled 1, 2,
3, ..., and columns
are labeled X, Y, Z. Note, for variables, X1, Y1, Z1, X2, Y2, Z2, ...,
where no separator is evident, use sep = "". Any illogical separation
argument will result in unlabeled
variables. If sep = NULL (the default), unlabeled variables are forced.
This is a good idea if the original matrix
has landmarks out of order (as the the landmark labels might not sort as
expected).