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Version 1.9 Build 1367

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Basic Mapping

This section presents a simple comparison key to accessing information in flat tables versus a MeasurementSet. The following table summarizes the conversion; the Flat Table Column is the table keyword used in flat tables and the MeasurementSet Column is the corresponding keyword while Table specifies whether the information exists in the main table or in a subtable. Data information in the ``main'' table is invoked normally:

- a := table('example.MS');
- scans := a.getcol('SCAN_NUMBER');

Data information in subtables is accessed by adding a subdirectory to the MeasurementSet descriptor:

- a := table('example.MS/SOURCE');
- object := a.getcol('NAME');

Flat Table Column	MeasurementSet Column	Table
Time	TIMEa	main
DATA	FLOAT_DATAb	main
SCAN	SCAN_NUMBER	main
SUBSCAN	NS_GBT_SUBSCAN	main
RECEIVER_ID	RCVRID	NS_GBT_BACKEND
OBJECT	NAME	SOURCE
PSRDM	PSRDM	NS_GBT_BACKEND
PHASE_ID	NS_GBT_PHASE_ID	main
UTCSTART	TIMEa	main
UTDATE	TIMEa	main
PHASETIM	PHASETIM	NS_GBT_BACKEND
FREQRES	RESOLUTION	SPECTRAL_WINDOW
OBSFREQ	REF_FREQUENCY	SPECTRAL_WINDOW
RFSIDE	RFSIDE	NS_GBT_BACKEND
IFSIDE	IFSIDE	NS_GBT_BACKEND
IFF	IFF	NS_GBT_BACKEND
CAL	CAL	NS_GBT_BACKEND
SIGREF	SIGREF	NS_GBT_BACKEND
PHASETIM	PHASETIM	NS_GBT_BACKEND
BLANKTIM	BLANKTIM	NS_GBT_BACKEND

^a In MeasurementSets, the TIME is in UTC seconds. To convert to flat table Time:

- a := table('example.MS');	# Get the table into Glish.
- b := a.getcol('TIME');	# Get the TIME column.
- c := dm.unit(b[1],'s');	# Add the units explicity.
- d := dm.epoch('utc',c)	# Define the epoch.
- e := d.m0.value		# e will be the 'Time' from the flat table.

To get UTDATE, use the 'r_utc' reference code in the dm.epoch command.

^b DATA is a 2-dimensional array while FLOAT_DATA is a 3 dimensional array. (e.g. if data::shape is [256,1357], then float_data::shape will be [1,256,1357].