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Getting started with PLT

Typing HElp at the ``PLT>'' prompt will provide you with help concerning the PLT commands. The PLT interactive help is used in exactly the same way as the XSPEC help. If you wish to read the interactive help on PLT without running the PLT routine, you should use the (system level) XHELP PLT command.

The most common command used in PLT is Rescale. Using Rescale X followed by two numbers, will set the minimum and maximum of the plotted x-range to the numbers specified. If you type Rescale X (with no arguments), the minimum and maximum values will be reset to their default values. Likewise, Rescale Y can be used to set the y-range.

Most PLT commands do not cause the screen to be updated the way the Rescale command does, thus allowing you to make several changes to the the graph without having to wait for the screen to be updated after every change. If, at any time, you wish to see what the current graph looks like, enter the Plot command, which will cause the display to be redrawn.

The LAbel command can be used to add labels to various locations on the graph. For example, typing LAbel Top EXOSAT was great will cause the message `EXOSAT was great' to appear at the top of the graph the next time the display is redrawn. The command LAbel Top followed by a return will remove that message.

The Hardcopy command is used create a file that can later be printed. Hardcopy does not reproduce what currently is visible on the graphics display, but rather what you would see if you re-issued the Plot command. The command Hardcopy ? can be used to see what the default hardcopy device is. If you do not like the default, you can override it. For example, assume that your version of PGPLOT supports the QMS device. To generate a file suitable for printing on a QMS printer you would enter Hardcopy /QMS and a PGPLOT.QMPLOT file will be generated in your current directory. Many sites have created a system-wide indirect file that will both create the hardcopy file, and then immediately print it. If you are at one of these sites, then @HARD will directly produce a plot on the printer.

In PLT it is possible to fit models to the displayed data. However, it is important to remember that PLT does not fold the model through the detector response, and therefore, PLT models should not be used to fit X-ray spectra.

To exit PLT and return to the XSPEC level, enter the PLT EXit command. When you return to XSPEC, any changes that you made to the plot will be forgotten.

next up [*] [*]
Next: Fitting with few counts/bin Up: Overview of PLT Previous: XSPEC graphics
Ben Dorman