# spline(1)

## NAME

spline - interpolate smooth curve

## SYNOPSIS

spline [-aknpx] ...

## DESCRIPTION

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, *Numerical* *Methods* *for* *Scientists* *and*
*Engineers*,2nd ed., 349ff) has two continuous derivatives,
and sufficiently many points to look smooth when plotted,
for example by **graph(1)**.

## OPTIONS

-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, that is, 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).

## ATTRIBUTES

See **attributes(5)** for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________*|*_____________________________*|*
| Availability | SUNWesu |
|_____________________________*|*_____________________________*|*

## SEE ALSO

**graph(1)**, **attributes(5)**
R. W. Hamming, *Numerical* *Methods* *for* *Scientists* *and*
*Engineers*, 2nd ed.

## DIAGNOSTICS

When data is not strictly monotonic in *x*, spline reproduces
the input without interpolating extra points.

## BUGS

A limit of 1000 input points is enforced silently.

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