RPLOT geometric integral operators, e.g. VOLUME INTEGRAL,
are computed using time dependent metric information 
generated by the main code run (if available), unless
information from the run indicates that a time independent
concentric circular geometry was used, in which case 
metric information is generated analytically.

The default starting location for all integrals is the 
magnetic axis (r/a = 0); however this default can be
overridden by the user.  Selection of integral is done
via an integer "opcode" i; specifying -i causes RPLOT
to prompt for a non-default lower integration limit.

The integration upper limit subsequently becomes either
an independent coordinate (axis) or a constant depending on
the plot type requested.

Integral operators sometimes imply a units change on the
y axis of the data to be plotted; if this units change 
cannot be resolved from a table of standard transformations,
the user is prompted for a y axis units label.

(this note written by D. McCune 19-Oct-1987 PPL x2731)