Description

listobs task: List the summary of a data set in the logger or in a file

This application reports various metadata related to an MS. The listing is sent to the logger or can be saved to a file. Standard MS selection parameters can be used to limit the listing (see Visibility Data Selections for details).

The report begins with information such as the observer, the project ID, the number of records, the length of the observation, and minimum and maxiumum timestamp of the records included. Following this are several tables summarizing metadata. There is a table which summarizes scan data (only if verbose = True), a table that summarizes field data, a table that summarizes spectral window data, a table that summarizes source data (only if verbose = True), and a table that summarizes antenna data. If verbose = False, the antenna summary will only list antenna and station names. If verbose = True, additional information such as the diameter, latitude and longitude, position relative to the array center, and the ITRF geocentric coordinates for each antenna will be listed.

Should the MS have multiple array IDs and/or multiple observation IDs, the report will list all of these tables for each array ID/observation ID pair.

Note: The 'Average Interval (s)' column in the scan table is the average of the MS's INTERVAL column for each scan.

 

Description of algorithm to calculate the number of unflagged rows

The number of unflagged rows is only computed and reported in the scan and field table if listunfl=True. Computing these quantities can have a negative performance impact, especially for large datasets. The number of unflagged rows (the nUnflRows columns in the scans and fields portions of the listing) is calculated by summing the fractional unflagged bandwidth for each row (and hence why the number of unflagged rows, in general, is not an integer). Thus a row which has half of its total bandwidth flagged contributes 0.5 rows to the unflagged row count. A row with 20 of 32 channels of homogeneous width contributes 20/32 = 0.625 rows to the unflagged row count. A row with a value of False in the FLAG_ROW column is not counted in the number of unflagged rows.

Parameter Summary

vis

The measurement set to interrogate.

selectdata

Select a subset of data?

field

Field selection. Used only if selectdata = True.

spw

Spectral window selection. Used only if selectdata = True.

antenna

Antenna selection. Used only if selectdata = True.

timerange

Timerange selection. Used only if selectdata = True.

correlation

Correlation selection. Used only if selectdata = True.

scan

Scan selection. Used only if selectdata = True.

intent

Intent selection. Used only if selectdata = True.

feed

Feed selection. Used only if selectdata = True.

array

Array selection. Used only if selectdata = True.

uvrange

The uvrange selection. Used only if selectdata = True.

observation

Observation selection. Used only if selectdata = True.

verbose

Verbosity level. True prints more than false.

listfile

File name to which to save report. No file is produced if set to the empty string.

overwrite

Overwrite the specified file if it exists? Only used if listfile is not the empty string.

listunfl

Include number of unflagged rows in the field table?

cachesize

Experimental parameter allowing user to control the temporary cache size in which data are stored so they do not have to be recomputed. 50 MB (the default) appears to be a reasonable value for most cases.