PLOT UTILITY by  Ron Wiesen 6/2/91

Described is a utility "Plotter". It is in BASIC and it is file"PLOT.DO". It requires the "Backbone" utility manager. File "UTIL.DO" is the Backbone.

Plotter plots numeric values on the Liquid Crystal Display (LCD) in either Y-only mode or Y&X mode. Y-only mode plots each value as a vertical Y coordinate at the next LCD horizontal position, for up to 240 points (240 horizontal positions). Y&X mode plots one point on the LCD per pair of Y and X coordinates, thus the number of points that are plotted is only limited by the amount of available numeric data.

        Command Syntax and Arguments
The Plotter command syntax can have up to 10 arguments. This is shown below; arguments that are shown as all capitalized are literal, arguments within braces [] are optional. Command syntax:
PLOT [buf#] [Yb] [Yt] [Xl] [Xr] [Yo] [Xo] [dot] [over]

Arg symbol description
1   PLOT   command name of Plotter
2   [buf#] buffer number of open file  that contains plot data. Action per sign:
  positive - plots and increments U% for             each point plotted
  0 (nul)  - no plot, sets defaults                  and overwrites them per                 other arguments
  negative - plots (U% unaffected)
3   [Yb]   Y limit for bottom LCD edge
4   [Yt]   Y limit for top    LCD edge
  Yb and Yt must differ
5   [Xl]   X limit for left   LCD edge
6   [Xr]   X limit for right  LCD edge
  If Xl and Xr differ, Y&X mode
7   [Yo]   Y origin; vertical   Y axis
8   [Xo]   X origin; horizontal X axis
  If Yo or Xo not nul, origin is set
9   [dot]  plots as dots, not as a line
10  [over] plots over prior LCD display
  If dot/over not nul or 0, function on

        Example Call to Plotter
10 N$="PLOT -5 -1 1 3.5 -3.5 0 0":GOSUB
The example above plots from file buffer #5, within bottom/top limits of -1/+1, in Y&X mode within left/right limits of +3.5/-3.5, draws Y/X origin lines that cross at 0/0, and does not alter variable U%. Note: dot and keep functions are per prior PLOT call or per default.

        Utility/Backbone Particulars
The Plotter line numbers are shown below:
  LINE 65101 - Backbone/Plotter link
  LINE 65201 ... 65234 - program area
  LINE 65514 - Plotter error DATA

The Plotter has four errors. The error numbers and error text are shown below:
  101 "bottom & top Y BOUNDS are EQUAL"
  102 "read Y OK, End of File on X"
  103 "Y Out of Bounds"
  104 "X Out of Bounds"

        Array/Variable Usage
The Plotter uses one-letter string array as shown below:
  U$()  - parsed command string. Structure:
U$(0)  - number of arguments
U$(1)  - PLOT
u$(2)  - [2nd ARGUMENT]
 ... 
U$(10) - [10th ARGUMENT]

The Plotter uses one-letter double-precision array as shown below:
  U#() - numeric equivalent of U$()

The Plotter uses two-letter integer array as shown below:
  UU%(UB%) - plot point count to user. Backbone transfers it to U% on return to user.

The Plotter uses two-letter double-precision variables as shown below:
  UI# - delta Y
  UJ# - delta X
  UK# - Y/X
  UL# - normalized Y/X (0 to 1)
  UN# - Y/X limit

The Plotter uses two-letter integer variables as shown below:
  UB% - utility nest level
  UI% ... UJ% - general purposes.
  UK% - Y&X mode flag
  UL% - plot point counter
  UP% - Y/X out of bounds flag