Plot the File

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Plot the File

Once you have created a version of DEMO.QDP, you can run QDP with

(If QDP fails to run, then you might need to define the QDP symbol as described in Appendix D, Installation Guide.) It is not necessary to enter the .QDP extension as the QDP program assumes that as the default. When the program starts, you will receive the following message:
To produce plot, please enter
PGPLOT file/type:
You should enter the PGPLOT specification for the device on which you wish to plot. If you do not know the device name, then enter ? and all the device types supported by your local version of PGPLOT will be listed. If your terminal supports Tektronix graphics, then enter /TE to make the plot appear on your terminal. You might also try /RE for Retrographics. Most Tektronix emulators support the Retrographics extensions that allow the software to toggle between text and graphics modes.

A graph containing two lines will now be drawn as illustrated in figure 2.1.

  graph containing two lines
Figure 2.1: The default appearance of the DEMO.QDP file.

Since the file contained three columns of numbers, the default mode assumes there are three plot groups. The first plot group determines the x coordinate. The next two columns are plotted as two lines. On a color display the first line will be red and the second green, which are the default colors for plot groups 2 and 3. The name of the QDP file appears in the top left of the plot and your userid, current date, and time appear in the bottom right of the plot. The PLT> prompt will now appear. In the following sections you will see how to enter various commands to change the default plot. The most useful command for beginners is the HElp command, which can be used to get instructions on how to use any command.

Another useful command is EXit that will get you out of the PLT subroutine. If you are in QDP, control will be returned to the operating system; in other programs, control will be returned to the calling program.

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Next: Rescaling Up: Basics Previous: QDP Files

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