Plotting Your Data - HP 7470A Interfacing And Programming Manual

plotting without a pen until it encounters an SP command. You can
lessen the manual intervention by storing the pen using SPOas the last
HP-GL instruction before any pause, and by issuing a pen select
command as the first HP—GL instruction after the pause.
Program lines to pause, change pens, and title the graph using a wide
pen follow. Remember when you run the complete program to remove
the old pens and load wide pens directly into the left and right stalls
when the message appears. The SP1 command here, the first command
after the program pause, assures that the pen holder is loaded so all
subsequent lines will be drawn.
200 PRINT "SPO;"
210 UISP "CHHNGE TU NIUE FEMS"
220 PHUSE
230 DISP " "
240 PRINT "SP1 PH6,15O SI.4,.B CF-S.S,2.0"
250 PRINT "LB1S81 SHLES BY REGIUNE"
Plotting Your Data
We are now ready to draw lines. Each of the four data lines on this
graph is drawn using a different technique. The first two lines are
drawn by plot commands with parameters included when the program
was written. Hence, if the data changes, it will be necessary to change
the plot commands in the program.
The first line (the bottom-most line on the graph) is drawn with pen 1
using a dashed line type. The program takes full advantage of the
plotter's relatively free syntax and uses spaces to delineate parameters.
Send the character strings to the plotter exactly as shown. Be sure to
enter those spaces; if the spaces are removed, the plotter will try to plot
one very large number and you won't plot the line.
After drawing the line, the pen moves to the legend area below the
graph title and draws a short line. The PU command causes the line
type pattern to begin again at the beginning of this line.
The second line is also plotted using plot commands with fixed parame­
ters. These plot commands use the stricter syntax of the 9872 or 7225
plotters and would be accepted by any HP plotter programmed in
HP—GL. The line type used consists of long and short dashes; the line is
drawn with pen 2. After the data are plotted, the corresponding line is
drawn in the legend.
8-6 PUTTING THE COMMANDS TO WORK