derive a new difference matrix from an old difference matrix by merging or deleting
items

**-d**- disable check for duplicates
**-o***filename*- output file

This program can be used to quickly derive a smaller difference matrix
from a larger one, without having to rerun the lengthy calculations that
were needed to derive the initial difference matrix.

Say, you have used the Levenshtein program to
derive a difference table for six items, labelled *A* to
*F*. If you join these in two items, *ABC* and *DEF*, the
distance between those two items will be much less accurate than if you
had run the Levenshtein program on data that was already joined into two
groups, *ABC* and *DEF*.

You can use locmod to derive the corresponding
file with coordinates.