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: http://www.atnf.csiro.au/computing/software/asap/userguide/node19.html
Дата изменения: Unknown Дата индексирования: Tue Feb 5 07:52:09 2013 Кодировка: Поисковые слова: eta carinae |
ASAP contains flexible data selection. Data can be selected based on IF, beam, polarisation, scan number as well as values such as Tsys. Advanced users can also make use of the AIPS++ TAQL language to create selections based on almost any of the values recorded.
Selection is based on a selector object. This object is created and various selection functions applied to it (set_ifs, set_beams etc). The selection object then must be applied to a scantable using the set_selection function. A single selection object can be created and setup then applied to multiple scantables.
Once a selection has been applied, all following functions will only ``see'' the selected spectra (including functions such as summary). The selection can then be reset and all spectra are visible. Note that if functions such as copy are run on a scantable with active selection, only the selected spectra are copied.
The common selection functions are:
set_beams | Select beams by index number |
set_ifs | Select ifs by index number |
set_name | Select by source name. Can contain ``*'' as a wildcard, e.g. ``Orion*_R''. |
set_ifs | Select IFs by index number |
set_polarisation | Select by polarisation index or name. If polarisation names are given, the data will be on-the-fly onverted (for example from linears to Stokes). |
set_query | Set query directly. For power users only! |
set_tsys | Select data based on Tsys. Also example of user definable query. |
reset | Reset the selection to include all spectra. |
Note that all indices are zero based.
Examples:
ASAP>selection = selector() # Create selection object ASAP>selection.set_ifs(0) # Just select the first IF ASAP>scans.set_selection(selection) # Apply the selection ASAP>print scans # Will just show the first IF ASAP>selection.set_ifs([0,1]) # Select the first two IFs ASAP>selection.set_beams([1,3,5]) # Also select three of the beams ASAP>scans.set_selection(selection) # Apply the selection ASAP>selection.set_name('G308*') # Select by source name ASAP>selection.reset() # Turn off selection ASAP>scans.set_selection(selection) # Apply the reset selection ASAP>scans.set_selection() # alternative to reset selection
Malte Marquarding 2007-08-16