Compute the changes in the dispersion function for several APS lattices:
sddschanges APS.twi APS.changes -copy=s -changesIn=betax,betay,etax
The output file in this example would have one fewer pages than the input
file. Each page would contain the column s from the first page, along with
the differences from the first page for betax, betay, and etax.
One could also compute the changes relative to the nominal lattice:
sddschanges APS.twi -baseline=APS0.twi APS.changes -copy=s -changeIn=betax,betay,etax
The output file would have one page for every page in the input.