SPLINE(1G)               DOMAIN/IX SYS5                SPLINE(1G)



NAME
     spline - interpolate smooth curve

USAGE
     spline [ options ]

DESCRIPTION
     Spline takes pairs of numbers from the standard input as
     abscissas and ordinates of a function.  It produces a simi-
     lar 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., pp. 349ff) has two continuous deriva-
     tives, and sufficiently many points to look smooth when
     plotted, for example by graph(1G).

OPTIONS
     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'' = ky'',    y'' = ky''
          is set0by the1next arg
nument (
n-
d1
efault 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 abscissas start at lower limit (default 0).

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

NOTES
     A limit of 1,000 input points is enforced silently.

RELATED INFORMATION
     graph(1G).





Printed 12/4/86                                          SPLINE-1