spline(1g)
NAME
spline − interpolate smooth curve
SYNTAX
spline [ option ] ...
DESCRIPTION
The spline command 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 has two continuous derivatives, and a sufficient number of points to look smooth when plotted.
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
y′′0=ky′′1,y′′n=ky′′n−1
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, meaning to 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).
RESTRICTIONS
A limit of 1000 input points is enforced silently.
DIAGNOSTICS
When data is not strictly monotone in x, spline reproduces the input without interpolating extra points.