SPLINE(1G-BSD)    MISC. REFERENCE MANUAL PAGES     SPLINE(1G-BSD)



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(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
     plot(1G)

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.




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