# 32v 1m spline

SPLINE(1G) UNIX Programmer's Manual 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 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).

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** limits. Normally these limits are calculated from the data. Automatic abcissas start at lower limit (default 0).

## SEE ALSO

## 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.