C.15. - spline.4
Spline.4 creates data points at evenly spaced intervals using a cubic spline algorithm to interpolate new points from the old. The interpolated points lie on a cubic polynomial between each pair of original points, and each polynomial section is joined continuously to the next with continuous first and second derivatives.
fn spline.4 fn spline.4 [+s|-s] [[n=]npts] [f=from] [t=to] or fn . .The default
from
and
to
values are the first and last
values of
x
in the original data.
If you don't enter arguments,
you will be prompted for the number of points and the range to interpolate
over.
The
+s and
-s options turn the automatic sorting and merging
of data on and off.
Data must be in increasing order, by
x,
for the spline to succeed.
Also,
x
values must be distinct.
Turning the sort off saves time for splining presorted data.
The default
is no sort.
Spline.4 turns off error-bar mode and error-bar values are ignored in the sorting.