15.64.52.1  X,y   - Set the overall size of the plot The final size is the
selected size plus the margins.  The actual size of the  plot  depends  on
the  device  you  are using.  The x,y are the size of the TEXT system.  If
the final size plus margins is  larger  than  the  physical  size  of  the
display,  the  plot is automatically reduced to fit.  If the final size is
smaller than the physical size of the device, the  plot  plus  margins  is
centered.