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A scantable has header information and data (a scantable is actually an AIPS++ Table and it is generally stored in memory when you are manipulating it with ASAP. You can save it to disk and then browse it with the AIPS++ Table browser if you know how to do that !).

The data are stored in columns (the length of a column is the number of rows/spectra of course).

Two important columns are those that describe the frequency setup. We mention them explicitly here because you need to be able to understand the presentation of the frequency information and possibly how to manipulate it.

These columns are called FREQ_ID and MOLECULE_ID. They contain indices, for each IF, pointing into tables with all of the frequency and rest-frequency information for that integration.

There are of course many other columns which contain the actual spectra, the flags, the Tsys, the source names and so on.

There is also a function summary to list a summary of the scantable. You will find this very useful.

Example:

  ASAP>scans = scantable('MyData.rpf')
  ASAP>scans.summary()                # Brief listing

  # Equivalent to brief summary function call
  ASAP>print scans

The summary function gives you a scan-based summary, presenting the scantable as a cascading view of Beams and IFs. Note that the output of summary is redirected into your current pager specified by the $PAGER environment variable. If you find the screen is reset to the original state when summary is finished (i.e. the output from summary disappears), you may need to set the $LESS environment variable to include the -X option.

Malte Marquarding 2007-08-16