Ian M George: Quick Guide to QDP

These pages are unofficial in all respects. They are primarily simply notes to myself. The information is not guaranteed to be correct or up-to-date.

QDP is a plotting package written by Allyn F. Tennant at NASA/MSFC. It takes an ASCII file as input. This ASCII file contains the data to be plotted, but can also contain 'commands' to control what is plotted, and how. After reading in the data (& commands) one is (usually) left in a command-line-driven, interactive plotting mode.

The actual plotting is performed by a set of subroutines (known a plt - hence the standard PLT> prompt one gets when QDP is fired up).

QDP provide a powerful set of commands suitable for producing publication-quality plot. A full QDP manual is available online, and an interactive 'help' facility is provided within QDP. Below we simply list a few common commands for novice users.

To fire-up QDP:

qdp {filename}

Note that QDP is also the plotting package used by the xspec spectral analysis package, the FTOOL fplot, and various other applications. (Basically if you see the PLT> prompt, you're in QDP.)

The PGPLOT file/type: prompt:

PGPLOT file/type: /xw

for a standard xterm window [or type ? at the prompt for a list of alternatives].

Common Commands (typed at the PLT> prompt):

quit quit QDP
help fire-up QDP interactive help
plot replot the graph
rescale x 1.0 2.5 rescale the x-axis between 1.0 and 2.5
(similarly rescale y -1e-3 2.3e2)
log x plot the x-axis in log-space
(similarly log y)
info list info on 'vectors' in file
co off 2 don't plot "vector" 2
(opposite is co on 2)
err off 3 don't plot errors for "vector" 3
(opposite is err on 3)
hard /cps write color PS file of plot
(file will be called pgplot.ps)

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