4.3BSD-UWisc/man/cat1/spline.1g

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 12/27/86         April 29, 1985                         1