SPLINE(1G) UNIX Programmer's Manual SPLINE(1G)
NAME
spline - interpolate smooth curve
SYNOPSIS
spline [ option ] ...
DESCRIPTION
_S_p_l_i_n_e 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, _N_u_m_e_r_i_c_a_l _M_e_t_h_o_d_s _f_o_r _S_c_i_e_n_t_i_s_t_s _a_n_d
_E_n_g_i_n_e_e_r_s, 2nd ed., 349ff) has two continuous derivatives,
and sufficiently many points to look smooth when plotted,
for example by _g_r_a_p_h(1G).
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
graph(1G), plot(1G)
DIAGNOSTICS
When data is not strictly monotone in _x, _s_p_l_i_n_e reproduces
the input without interpolating extra points.
BUGS
A limit of 1000 input points is enforced silently.
Printed 11/26/99 April 29, 1985 1