# spline(C)

**spline --
interpolate a smooth curve from a set of points
**

## Syntax

**spline**
[ **-a** *m* ]
[ **-k** *k* ]
[ **-n** *n* ]
[ **-p** ]
[ **-x** *l* [ *u* ] ]
## Description

**spline** reads pairs of numbers from the standard input
as the abscissa and ordinate values (x and y coordinates)
of a function.
It produces a similar set, approximately equally spaced and
including the input set, on the standard output.
The cubic spline output has two continuous derivatives,
and enough points to look smooth when plotted.
**spline** accepts the following options,
each as a separate argument:

**-a** *m*-
Supplies abscissa (x-axis) values automatically
with a spacing of
*m* if they are missing from the input.
The default spacing is 1.

**-k** *k*-
Sets the constant used in boundary value computation
to
*k*; the second derivative at each boundary is set to
*k* times the adjacent first derivative.
The default value of *k* is 0.0 which gives a natural cubic spline
with a zero second derivative on both its boundaries.

**-n** *n*-
Spaces output points so that approximately
*n*
intervals occur between the lower and upper limits defined
for the abscissa (x-axis) by **-x**.
The default number of intervals is 100.

**-p**-
Makes the output periodic: that is,
**spline** matches derivatives
at each end.
First and last input values should normally have the same value.

**-x** *l* [ *u* ]-
Defines the lower (
*l*) and upper (*u*) limits on
the abscissa (x-axis).
Normally these limits are calculated from the data with a
default lower limit of 0.

## Limitations

If the data does not increase monotonically along the x-axis,
**spline** reproduces the input without interpolating extra points.
The input data is limited to 1000 points.

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© 2003 Caldera International, Inc. All rights reserved.
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SCO OpenServer Release 5.0.7 -- 11 February 2003