Hatching A Bar - HP 7470A Interfacing And Programming Manual

Plot showing filled bar
I J |
J F M A M
Hatching a Bar
The following program segment, together with lines 10 to 100 and 400
of this chapter's program, hatches a bar which represents February
data for line 2, i.e., 2,50. The XT instruction was deleted from line 70 to
omit drawing the X-ticks. Again the bar is centered over the X data
point. In this segment, the increment variable P is the distance between
hatching lines and determines whether a wide or narrow hatch pattern
is drawn. Youmay want to make further refinements depending on pen
width and bar width and height. The bars are shown here actual size
with P set at 100 and 300. The locations of the variables are shown on
the first bar and should help you understand the program listing.
For plots on transparency film or to make hatch lines more uniform,
you should slow the pen Velocityusing the VS instruction.
The routine performs the following tasks.
1. and 2. (Same as solid fill algorithm.)
3. Using the output obtained in step 1, sets the window to be the bar we
wish to hatch.
4. Beginning the width of the bar below the Yminvalue, plots a line at a
45 degree angle to the opposite side of the bar, increments the
Y-Valueand continues the process until the top of the bar is reached.
5. Resets the scaling and window to their previous values.
8-12 PUTTING THE COMMANDS TO WORK