Getting the data

First read the data with the command read-gsd-data:

$>\!>$ r-g-d

and SPECX will ask you which data file you want to read with the following question:

GSD scan number? [ ]

Give it just the relevant part of the scan number. For example, to read obs_das_0030.dat, one would type the following:

$>\!>$ r-g-d

and answer the question with 30

You could type it all on one line:

$>\!>$ r-g-d 30

and avoid the dialogue.

In this simple example, I have been at pains illustrate in considerable detail the character of SPECX commands and the nature of the dialogue. In most of the following material this level of detail will be omitted. Generally, SPECX commands are self-explanatory as a result of the amount of subsidiary verbage.

An Aside

How to specify scans observed in groups -- In many cases, you will have observed several points in a sequence using the GRID, PATTERN or RASTER observing modes. In such cases, all the spectra observed in this way are grouped together in a single GSD file under a single scan number, and each spectrum is also defined by a sequence number (set by the order in which it was observed) as well as the scan number. Thus

$>\!>$ r-g-d 30 4

will load spectrum sequence number 4 from observation 30.

Now you want to look at the spectrum. Just do;

$>\!>$ n

`n' stands for `start up new plot file'; not exactly obvious, but it makes sense once you are used to it. Actually, it's a little more subtle than that; the full command is

$>\!>$ new-plot

and this command requires two variables to be input; pen width and colour. `n' alone has been defined as equivalent to `new-plot 1 3'.

All this assumes that the plot device is set to `terminal'. If it's not, and that's the way you want it, first type

$>\!>$ s-p-d t

before typing n again. If you have turned on the interactive mode (the default on starting SPECX6.7 for the first time is non-interactive, an improvement over Version 6.3), then to get out of the plot hit the `e' for exit.

A typical spectrum looks like that shown in Figure .

Figure: A typical spectrum; in this case the scales of the axes have been set to display the result to good advantage. Below the plot frame, most of the information which might be needed is present.

The spectrum can be plotted in two ways: histogram (the default on startup), and line (connect the dots). One can also set the line thickness and the colour (set to 1 and 3 [=green] on startup). The first two are controlled by the flags histogram and line_weight. That is, on startup the defaults are

$>\!>$ histogram=true
$>\!>$ line_weight=1

Typing histogram=false gives a line plot. I wouldn't recommend using a line_weight larger than 3. Colour numbers range from 1 to 15.