Help System (web edition)

XSCALE2=XSCALE or XSCALE2=<list of values:labels> 
(in PLOT operation for diagrams and curves)
specifies a secondary X scale above the graph (in the top margin).
In case XSCALE2=XSCALE this secondary scale is exactly same as XSCALE.
In the case of a list of scale values:labels (:label is optional)
the points of the secondary scale are selected from this list and
located according to XSCALE. Use of labels in XSCALE2 permits another
notation for the scale values.

YSCALE2 works similarly on the basis of YSCALE and places a secondary
Y scale in the right margin.

Also ticks may be set on XSCALE2 and YSCALE2 by TICK2=<x step>,<y step>.
TICK2=TICK selects identical ticks.
  P = more information on plotting