spline(1G) DG/UX 4.31 spline(1G)
NAME
spline - interpolate smooth curve
SYNOPSIS
spline [-a [spc]] [-k const] [-n interval] [-p] [-x [lower
[upper]]]
spc Horizontal spacing; default = 1
const A numeric constant
interval Number of intervals between lower and upper limits
lower Lower limit of the abscissa; default = 0
upper Upper limit of the abscissa
DESCRIPTION
Spline takes pairs of numbers from the standard input as
abscissas and ordinates of a function. It produces a
similar 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
Scientists and Engineers, 2nd ed., 349ff) has two continuous
derivatives, and sufficiently many points to look smooth
when plotted.
Options are:
-a Supply abscissas automatically (they are missing from
the input); spacing is given by the next argument, or
is assumed to be 1.0 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. If n is
less then 1, or n is not integral, the default value is
used. (Default n = 100)
-p Make output periodic, i.e. match derivatives at ends.
First and last input values should normally agree.
-x The arguments, if present, represent the lower and
upper x limits, respectively. Normally these limits
are calculated from the data. If both are given, the
lower limit must be less than the upper limit or the
option is ignored. Automatic generation of the
abscissas start at the lower limit.
DIAGNOSTICS
When data is not strictly monotone in x, spline reproduces
the input without interpolating extra points. In the
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spline(1G) DG/UX 4.31 spline(1G)
absence of the -a option, if the last abscissa supplied does
not have a corresponding ordinate, it is ignored.
BUGS
A limit of 1000 input points is enforced silently.
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