You use the command GOVER to overlay a picture over an existing one drawn with GDISP or GPLOT.
However, the subsequent pictures are treated as independent entities so they
do not take into account the previous picture's layout.
In particular it is advisable to use the display parameter SCREL()
to adjust the size of the overlaid picture to the that of the previous one.

Basic overlay methods

   With the display parameters XREL() and/or YREL()
   you may place the subsequent pictures relative to the origin of the first one.
   Because the overall plotting area size is determined by the first picture
   you should plot the rightmost uppermost figure first. Example:

   GREAD right.gd
   GDISP / XREL(1.0) 
   GREAD left.gd
   GOVER / XREL(0.0)


   You may also use the display parameters XRSIZE() and/or YRSIZE()
   to allocate a plotting area with a size relative to the first picture's axes lengths:

   GREAD left.gd
   GDISP / XRSIZE(2.0)
   GREAD right.gd
   GOVER / XREL(1.0)


Insets

   You may also produce insets:

   GREAD bigpicture.gd
   GDISP
   GREAD smallinset.gd
   GOVER / XREL(0.25) YREL(0.25) SCREL(0.125)

   produces a small picture of 1/8 the size of the big one,
   located at an offset of 1/4 of the big picture's axes.

Fixed scale overlays

   By default each dataset is plotted with its own scale,
   Often this causes overlays with different axes.
   To improve on this you may specify (once per session)
   one of the following

   GMODE / FIXEDOVERLAY
   GMODE / FOVL

   In this case the scale of the preceeding GDISP command 
   is kept for all following GOVERs.
   To return to the startup default use one of the following

   GMODE / NOFIXEDOVERLAY
   GMODE / NOFOVL


Suppressing unwanted descriptions

   With the display parameters NOXNUM, NOYNUM and NOCOMMENT
   you can suppress unwanted axis descriptions:

   GREAD upper.gd
   GDISP / YREL(1.0) NOXNUM
   GREAD lower.gd
   GOVER / YREL(0.0) NOCOMMENT XNUM


   Sometimes axis tic numbers from different partial graphs overlap.
   You can suppress this by choosing slightly different display limits
   which have no visible effect but affect the tic numbering:

   GREAD right.gd
   GDISP / XREL(1.0) NOSP XMIN(0) XMAX(100)
   GREAD left.gd
   GOVER / XREL(0.0) NOSP XMIN(0) XMAX(99.9) SCREL(1)

   or

   GREAD right.gd
   GDISP / XREL(1.0) NOSP XMIN(0.01) XMAX(100)
   GREAD left.gd
   GOVER / XREL(0.0) NOSP XMIN(0) XMAX(100) SCREL(1)

   will plot data from 0 to 100 but avoids the overlap of the 0 and 100 tic numbers.


Complex pictures with EXEC

   Very complex pictures which require many commands are best built by
   grouping together the gd commands in a script file which can be
   executed with the EXEC command. This is also
   useful as a documentation how a particular figure was built.