3.2.1.0 table.queryC

NRAO Home > CASA > CasaRef

table.queryC - Function

3.2.1 Alternative table query function
Description

Make a table from a query applied to the current table. It is possible to specify column(s) and/or expressions to sort on and to specify the columns to be contained in the output table. See the example below. A new ”on-the-fly” table tool is returned. The new (reference) table can be given a name and will then be written to disk. Note that the resulting table is just a reference to the original table. One can make a deep copy of the query result using the copy function (see example).

Arguments


Inputs
query	the query expression
	allowed:	string
	Default:
resultTable	Name of the results table
	allowed:	string
	Default:
sortlist	Sort list of the results table
	allowed:	string
	Default:
columns	Columns to return in the sort table, leave blank for all
	allowed:	string
	Default:

Returns
casatable

Example

  tb.open("3C273XC1.MS")
  subt=tb.queryC("OBSERVATION_ID==0",
                sortlist="ARRAY_ID", columns="TIME, DATA, UVW")
  print subt.ncols()
# 23
  tb.close()
  copyt = subt.copy ("3C273XC1_spw1.MS", True)
  subt.close()
  copyt.close()

From the original table corresponding to the disk file 3C273XC1.MS, only rows with OBSERVATION_ID equal to 0 are selected and sorted by ARRAY_ID. Only the columns TIME DATA UVW are written. Thereafter a deep copy of the result is made. The table queryC command is equivalent to:

  SELECT TIME, DATA, UVW
  FROM 3C273XC1.MS
  WHERE OBSERVATION_ID==0
  ORDERBY ARRAY_ID

Example

The sortlist argument can be used to sort in ascending or descending order (or a mix of them) on one or more columns. Default is ascending. It is also possible to remove duplicate values using the word NODUPLICATES at the beginning.

E.g.:

  sortlist=’TIME desc’
  sortlist=’noduplicates ANTENNA1,ANTENNA2’
  sortlist=’ANTENNA1 desc, ANTENNA2 asc’
  sortlist=’desc ANTENNA1, ANTENNA2, TIME’

[next] [prev] [prev-tail] [front] [up]

Please send any comments or questions about CASA or AIPS++ to aips2-requests@nrao.edu

This code is available under the terms of the GNU General Public Lincense