To smooth a curve you should first reduce the number of points per set
by either `gr_reduce`, `gr_del_double` or `gr_spline` (with a small number of
output points). Afterwards the `gr_spline` curve is called with the number
of points needed.

gr_reduce -n 8 -last | gr_spline - 160 -arc

The `-last` Option in `gr_reduce` makes sure, that the last point of each
set is printed out in any case. This is needed, in this case it makes no
sense to loose the information of the curve endpoint. But, if using
`gr_spline` by default, without `-arc`, the spacing of the xknots is of
equal distribution which means, that the same number of points will be
calculated between to neighboured input points That would cause a point
accumaltion in the last interval.

Wed Jun 12 20:34:13 MET DST 1996