table - Module table

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3.2 table - Module table

Casapy interface to table system

  3.2.1 table - Tool
    table.fromascii - Function
    table.open - Function
    table.flush - Function
    table.fromASDM - Function
    table.resync - Function
    table.close - Function
    table.copy - Function
    table.copyrows - Function
    table.done - Function
    table.iswritable - Function
    table.endianformat - Function
    table.lock - Function
    table.unlock - Function
    table.datachanged - Function
    table.haslock - Function
    table.lockoptions - Function
    table.ismultiused - Function
    table.browse - Function
    table.name - Function
    table.toasciifmt - Function
    table.query - Function
    table.queryC - Function
    table.calc - Function
    table.selectrows - Function
    table.putinfo - Function
    table.addreadmeline - Function
    table.summary - Function
    table.colnames - Function
    table.rownumbers - Function
    table.setmaxcachesize - Function
    table.isscalarcol - Function
    table.isvarcol - Function
    table.coldatatype - Function
    table.colarraytype - Function
    table.ncols - Function
    table.nrows - Function
    table.addrows - Function
    table.removerows - Function
    table.addcols - Function
    table.renamecol - Function
    table.removecols - Function
    table.iscelldefined - Function
    table.getcell - Function
    table.getcellslice - Function
    table.getcol - Function
    table.getvarcol - Function
    table.getcolslice - Function
    table.putcell - Function
    table.putcellslice - Function
    table.putcol - Function
    table.putvarcol - Function
    table.putcolslice - Function
    table.getcolshapestring - Function
    table.getkeyword - Function
    table.getkeywords - Function
    table.getcolkeyword - Function
    table.getcolkeywords - Function
    table.putkeyword - Function
    table.putkeywords - Function
    table.putcolkeyword - Function
    table.putcolkeywords - Function
    table.removekeyword - Function
    table.removecolkeyword - Function
    table.getdminfo - Function
    table.keywordnames - Function
    table.fieldnames - Function
    table.colkeywordnames - Function
    table.colfieldnames - Function
    table.getdesc - Function
    table.getcoldesc - Function
    table.ok - Function
    table.clearlocks - Function
  3.2.2 tableplot - Tool
    tableplot.open - Function
    tableplot.setgui - Function
    tableplot.savefig - Function
    tableplot.selectdata - Function
    tableplot.plotdata - Function
    tableplot.iterplotstart - Function
    tableplot.replot - Function
    tableplot.iterplotnext - Function
    tableplot.iterplotstop - Function
    tableplot.markregions - Function
    tableplot.flagdata - Function
    tableplot.unflagdata - Function
    tableplot.locatedata - Function
    tableplot.clearflags - Function
    tableplot.saveflagversion - Function
    tableplot.restoreflagversion - Function
    tableplot.deleteflagversion - Function
    tableplot.getflagversionlist - Function
    tableplot.clearplot - Function
    tableplot.done - Function

Description CASA stores all data inside CASA tables which are stored on disk. A CASA table consists of an unlimited number of columns of data, with optional column keywords and optional table keywords. Columns are named and rows are numbered (starting at 0). The columns hold data, such as visibilities and uv coordinates, while the keywords hold general information such as units or revision numbers or table author or even other tables.

To make this concrete, examples of columns might be:

  U       V        W         TIME        ANT1   ANT2      VISIBILITY
124.011 54560.0  3477.1  43456789.0990    1      2        4.327 -0.1132
34561.0 45629.3  3900.5  43456789.0990    1      3        5.398 0.4521
....
....
....

and examples of keywords might be:

REVISION=2.01
AUTHOR="Tim Cornwell"
INSTRUMENT="VLA"

Everything in a CASA table (and thus all data stored in CASA) is potentially accessible and changable from casapy. The table module provides a convenient way of accessing and changing CASA tables from inside casapy. To do so one uses tb, the table tool, inside casapy. The table tool provides functions for:

Opening and copying of existing tables, (using open, and copy),
Get and put of table cells, columns and keywords,
Selection and sorting with TaQL (using the query or calc functions),
Get and put of table information strings,
Browsing of tables (using the browse function),
Printing of a summary of a table (using summary function),
Reading or writing a table from or to an ASCII format (using fromascii, and toasciifmt)

All operations are done inside the casapy client and are not written to disk until an explicit flush command is performed.

The most typical operation on a CASA table is to open it, load a column from the table into casapy, alter it using casapy capabilities, and then write it back to the table. For this only a few commands are relevant: see the example below.

Sorting and selecting of tables is possible. The table thus produced is a reference table, and points back to the original table.

Example

  tb.open(’3C273XC1.MS’)
  tb.summary();
  uvw=tb.getcol("UVW");
  tb.close()
  tb.open("3C273XC1.MS/SPECTRAL_WINDOW")
  freq=tb.getcell("REF_FREQUENCY", 0)
  tb.close()
  for i in range(len(uvw)):
    for j in range(len(uvw[0])):
       uvw[i][j] = uvw[i][j]*1.420E9/freq
  tb.open(’3C273XC1.MS’, nomodify=False)
  tb.putcol("UVW", uvw);
  tb.close()

See Also

tableplot

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