man(1) Manual page archive

     spline - interpolate smooth curve

     spline [ option ] ...

     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 Engi-
     neers, 2nd ed., 349ff) has two continuous derivatives, and
     sufficiently many points to look smooth when plotted, for
     example by plot (I).

     The following options are recognized, each as a separate

     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 points
          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).

     plot (I)

     M. D. McIlroy

     A limit of 1000 input points is enforced silently.