Chapter 4  PHILOSOPHY
 
TOPDRAWER  is  designed to plot and manipulate data.  It assumes that data
consists of X vs Y with errors DX, DY.  It may be X,Y  vs  Z  with  errors
DX,DY,DZ.   You  may  also specify NDX,NDY or NDZ the negative part of the
error bars separately from DX,DY or DZ.  The data may be  a  histogram  in
which  case  DX  would  be  the  bin width, or it may be a set of discrete
points with unrelated errors.  You may plot the data accordingly.

There  is  also an auxiliary set of coordinates, that may be used for data
manipulation, but not plotting.  They  are  U,DU,NDU,V,DV,NDV,W,DW,NDW  To
plot   the  data  in  these  coordinates  they  must  be  moved  to  X,Y,Z
coordinates.  This is easily done with the SWAP command.

The basic plotting operations are:
     1.  PLOT plots the data with optional error bars.
     2.  JOIN joins the data points with line segments.
     3.  HISTOGRAM plot the data as a histogram.
     4.  BAR plots the data as a bar chart (similar to a histogram)