table - Module

Description

AIPS++ stores all data inside AIPS++ tables which are stored on disk. An AIPS++ 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 1). 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 an AIPS++ table (and thus all data stored in AIPS++) is potentially accessible and changable from Glish. The table module provides a convenient way of accessing and changing AIPS++ tables from inside Glish. To do this one creates table tools inside Glish. The resulting tools can be operated on in various ways:

Opening, copying, renaming of existing tables, (using table, tablecopy, tablerename),
Get and put of table cells, columns and keywords,
Selection and sorting with TaQL (using the query tool function or calc tool function or tablecommand),
Iteration by subtables (using tableiterator),
Get and put of table information strings,
Access via table columns (using tablecolumn),
Access via table rows (using tablerow),
Indexed access (using tableindex),
Browsing of tables (using the browse tool function),
Printing of a summary of a table (using summary tool function),
Determine if a Glish value is a valid table (using is_table),
Writing or reading a table to or from an ASCII format (using tablefromascii, and toascii),
Reading a table from binary FITS format (using tablefromfits)

There is no tofits function available. It might get available in the future.

In addition this module contains a number of global functions related to tables, such as determining if a table exists (tableexists).

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

The most typical operation on an AIPS++ table is to open it by creating a table tool inside Glish, load a column from the table into Glish, alter it using Glish 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.

The Glish client handling all table events and operations is the tableserver. At startup of table.g the defaulttableserver is started which runs until the glish session ends. This server is by default used. It is, however, possible to start another one like:

  mytableserver:=tableserver();

and use that in the various constructors and functions taking a tableserver argument. In a similar way the defaulttableserver can be restarted in case it crashes in one way or another.

Example

  include "table.g"
  vis:=table("3C273XC1.MS", readonly=F);
  vis.summary();
  uvw:=vis.getcol("UVW");
  spw:=table("3C273XC1.MS/SPECTRAL_WINDOW", readonly=T);
  freq:=spw.getcell("REFERENCE_FREQUENCY", 1);
  uvw*:=(1.420E9/freq);
  vis.putcol("UVW", uvw);
  vis.close();

See Also
tablecolumn tablerow tableiterator tableindex

Aipsrc Variables

table.relinquish.reqautolocks.interval	nr of seconds to wait before relinquishing autolocks requested in another process
	Allowed:	float
	Default:	5
table.relinquish.allautolocks.interval	nr of seconds to wait before relinquishing all autolocks
	Allowed:	float
	Default:	60
table.endianformat	endian format to be used for storing data in new tables
	Allowed:	big,little,local
	Default:	big

Tools

table	Access tables from Glish
tablecolumn	Allows access to a column in a table
tablecomparer	Compare various aspects of two tables to see if they are equivalent
tableindex	Allows value based table access
tableiterator	Allows iteration through a table tool
tableplot	Plot data from tables via Glish
tablerow	Allows access to rows of a table tool

Functions

is_table Is this a valid table tool?

tablebrowser "Table browser"

tablecloseall close all open table tool objects

tablecommand Execute a table command

tablecopy copy a table

tablecreatearraycoldesc create descriptor of an array column

tablecreatedesc create a table descriptor

tablecreatescalarcoldesc create descriptor of a scalar column

tabledefinehypercolumn define a hypercolumn in a table descriptor

tabledelete delete a table

tabledemo Perform a demonstration: Not yet implemented

tableexists does this table exist on disk?

tableinfo return the info record

tableiswritable is this table writable?

tableopentables return names of open tables

tablerename rename a table

tabletest Perform a test

Next: table - Tool Up: Utility Previous: executivetest - Function Contents Index

is_table	Is this a valid table tool?
tablebrowser	"Table browser"
tablecloseall	close all open table tool objects
tablecommand	Execute a table command
tablecopy	copy a table
tablecreatearraycoldesc	create descriptor of an array column
tablecreatedesc	create a table descriptor
tablecreatescalarcoldesc	create descriptor of a scalar column
tabledefinehypercolumn	define a hypercolumn in a table descriptor
tabledelete	delete a table
tabledemo	Perform a demonstration: Not yet implemented
tableexists	does this table exist on disk?
tableinfo	return the info record
tableiswritable	is this table writable?
tableopentables	return names of open tables
tablerename	rename a table
tabletest	Perform a test