1 SPLINE
  Syntax:   SPLINE[/option] id [&idb]
            nknot
            knot1,knot2,...
            [&]idb2
            mode
   where:   option     is the type of spliine fitting
                       /HBOOK
                       /NAGLIB
                       /IMSL
            nknot      is the number of knots
            knot1      is the 1st knot position - not HBOOK verison
            knot2      is the 2nd knot position etc.
            [&]idb2    is the secondary id of the smoothed histogram
            mode       plotting mode - NAGLIB and IMSL versions only
  Defaults: idb2 = idb + 1, mode = 0,

  Spline fits a histogram. There are a number of possibilities
  available depending on whether you have the Naglib and/or IMSL
  libraries.  The default spline fitting type is NAGLIB (if
  available), IMSL (if available), HBOOK.

  The minimum number and maximum number of knots and their minimum and
  maximum values depend on the type of fitting - see the relevant
  section for details.

  The result of the fit will be put in a histogram with the same
  primary identifier as the input histogram and the secondary
  identifier you specify. The two modes are to store it as a smooth
  curve (errors on each point will be 0), or as a histogram with the
  same number of points as the input histogram (errors on each point
  will be the same as errors in the input histogram). Mode 0 is only
  available for IMSL and NAGLIB smoothing

  If you just give the command `SPLINE[/option] id' you enter into an
  interactive mode and can iterate on your fit by varying the numbers
  of knots and/or their positions. If you give the command this way in
  a macro then leave a blank line (or the command `YES') at the end of
  your fitting.

2 /HBOOK

  Uses the HBOOK routine HBSPLI1. You specify the number of knots, and
  the routine returns the chi**2 of the spline, but does not give you
  any control on the knot positions.  The errors on the bins are not
  taken into account..

2 /IMSL

  Uses the IMSL library routine ICSVKU. See the IMSL manual for
  complete details.  The number of knots must be at least 2 and the
  knots must be monotonically increasing. The first knot must be less
  than or equal to the first point in the histogram and the last knot
  must be greater than or equal to the last point in the histogram.

2 /NAGLIB

  Uses the NAGLIB library routine E02BAF. See the NAGLIB manual for
  complete details.  The number of knots must be less than or equal to
  the number of points - 4, and the knots must be monotonically
  increasing. The first knot must be greater than first point in the
  histogram and the last knot must be less than the last point in the
  histogram. The routine adds 4 knots at the minimum and maximum
  points.

  The errors on each point are taken into account.  Points with 0
  error are not included in the fit.  Use the `HIST ERROR id 0'
  command to remove the errors if you do not want to use them.
