SPLINE(1G) SPLINE(1G)
NAME
spline - interpolate smooth curve
SYNOPSIS
spline [ option ] ...
DESCRIPTION
Spline takes pairs of numbers from the standard input as
abcissas and ordinates of a function. It produces a simi-
lar set, which is approximately equally spaced and
includes the input set, on the standard output. The cubic
spline output (R. W. Hamming, Numerical Methods for Scien-
tists and Engineers, 2nd ed., 349ff) has two continuous
derivatives, and sufficiently many points to look smooth
when plotted, for example by graph(1).
The following options are recognized, each as a separate
argument.
-a Supply abscissas automatically (they are missing from
the input); spacing is given by the next argument, or
is assumed to be 1 if next argument is not a number.
-k The constant k used in the boundary value computation
(2nd deriv. at end) = k*(2nd deriv. next to end)
is set by the next argument. By default k = 0.
-n Space output points so that approximately n intervals
occur between the lower and upper x limits. (Default
n = 100.)
-p Make output periodic, i.e. match derivatives at ends.
First and last input values should normally agree.
-x Next 1 (or 2) arguments are lower (and upper) x lim-
its. Normally these limits are calculated from the
data. Automatic abcissas start at lower limit
(default 0).
SEE ALSO
graph(1)
DIAGNOSTICS
When data is not strictly monotone in x, spline reproduces
the input without interpolating extra points.
BUGS
A limit of 1000 input points is enforced silently.
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