V4/man/man6/spline.6

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.th SPLINE VI 10/20/73
.sh NAME
spline \*- interpolate smooth curve
.sh SYNOPSIS
.bd spline
[ option ] ...
.sh DESCRIPTION
.it Spline
takes pairs of numbers from the standard input as abcissas 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,
.ft I
Numerical Methods for Engineers and Scientists,
.ft R
2nd ed., 349ff)
has two continuous derivatives,
and sufficiently many points to look smooth when plotted, for
example by
.it plot
(I).
.s3
The following options are recognized,
each as a separate argument.
.s3
.lp +5 5
\fBa\fR	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.
.s3
.lp +5 5
\fBn\fR	Output approximately 
.it n
points, where
.it n
is given by the next argument.
(Default
.it n
= 100.)
.s3
.lp +5 5
\fBp\fR	Make output periodic, i.e. match
derivatives at ends.
First and last input values should normally agree.
.s3
.lp +5 5
\fBx\fR	Next 1 (or 2) arguments are lower (and upper) \fIx\fR limits.
.i0
.sh "SEE ALSO"
plot(I)
.sh AUTHOR
M. D. McIlroy
.sh BUGS
A limit of 1000 input points is enforced silently.