Browsing through MeasurementSets and Calibration Tables (browsetable)

Browse a table (MeasurementSet, calibration table, image)

The browsetable task is available for viewing data directly.  It handles all CASA tables, including MeasurementSets, calibration tables, and images. This task brings up a CASA Qt table browser, which can be launched from outside CASA using casabrowser.

browsetable is not required for normal data reduction but is useful for troubleshooting or for identifying table column names and formats. If you want to edit a long column or extract data for manipulation outside CASA (e.g. the uv data), see flagdata and the table tools in the Global Tool List.  The MeasurementSet columns and subtables are described here.

The default inputs for the CASA browsetable task are:

#In CASA
#   browsetable :: Browse a table (MS, calibration table, image)
tablename = ''             # Name of input table

Once the tablename is specified, available parameters include:

#   browsetable :: Browse a table (MS, calibration table, image)
tablename      =   'ngc5921_ut.ms' #  Name of input table
mightedit      =      False        #  Warning: the GUI seems to ignore whether the table
                                   #   tool is opened read-only - just be careful, esp.
                                   #   if filtering.
sortlist       =         ''        #  Columns to sort by (ascending)
taql           =         ''        #  TaQL query string for prefiltering the table.
skipcols       =         ''        #  Columns to omit

For more information about the Table Query Language (TaQL) string, see this note.

Example with tablename argument:

browsetable('ngc5921_ut.ms')

For an MS, as in this example, the table browser will display the MAIN table (Figure 1). To look at subtables, use the table keywords tab along the left side to bring up a panel with the subtables listed (Figure 2), then choose (double-click) a table name (Keyword) to display the subtable in a new tab (Figures 3 and 4). You can double-click on a cell in a table to view the contents (fourth figure below) then use the "Close" or "Close All" buttons at the bottom of the contents display to close one or all displayed values.


Type Figure 1
ID examination-fig-browser1
Caption The browser displays the MAIN table within a frame. You can scroll through the data with the sliders at right and bottom, and step through the pages with the "<<" and ">>" buttons or using "First" and "Last" to quickly advance to the beginning or end.  To go to a specific page, input the page number in the text box then click "Go".  By default, 1000 rows of the table are loaded at a time, but you can specify this setting in the "Loading ... rows" text box.
 
 
Type Figure 2
ID examination-fig-browser-subtables
Caption Use the "table keywords" tab to look at other tables within an MS. Double-click on a table name to view its contents in a new tab, as shown in the following figures.
 
Type Figure 3
ID examination-fig-browser-antenna
Caption Viewing the ANTENNA table of the MS.
 
Type Figure 4
ID examination-fig-browser-polarization
Caption The POLARIZATION table shows the number and types of correlations.  The CORR_TYPE integer array indicates the Stokes type as defined in the Stokes class enumeration.  Common types include RR (5), RL (6), LR (7), and LL (8) for circular polarization, and XX (9), XY (10), YX (11), and YY (12) for linear polarization.

Type Figure 5
ID examination-fig-browser-contents
Caption Double-click a cell in the table or sub-table to see its value displayed to the right.  Here, the DATA column cell (top right) contains a [2,63] array of complex numbers.  The WEIGHT_SPECTRUM for this data is shown below it as a [2,63] array of float values.  Use the sliders to see other values in the arrays, and click "Close" to close the cell contents display or "Close All" to close all contents displays.

Many options are available on the browsetable toolbar and menus:

  • To open a table, click the "Open Table" button or use the File > Open Table menu to open a file browser dialog box.
  • To close a table, click the "Close Table" button to close the table in the active tab, or use the options on the "File" menu to close the table in the active tab ("Close Table"), to select an open table to close ("Close..."), or to close all tables ("Close All").  You can also "Close All and Exit" the table browser.
  • To edit the table and its contents, click the "Edit Table" button or use the Edit > Edit Table menu.  You can also use the "Edit" menu to add a row to the table.  Be careful with this, and make a backup copy of the table before editing!
  • To view table information, click the "Table Information" (blue "i" button) or use the View > Table Information menu.  You can also hover the mouse pointer over the table name tab to get a popup with information.
  • To set a TaQL filter, click the "Filter on Fields" button or use the View > Filter on Fields menu.  This will open a "Filter Rules" dialog box within the table browser in which to set the filter.  Another option is to use the taql parameter in the browsetable() call.
  • To choose which columns to display, use View > Columns to select the columns from a list, which you can select individually or toggle with "Show All Columns" or "Hide All Columns".  Another option is to use the skipcols parameter in the browsetable() call.
  • To format the contents of the column cells, use View > Format Display to select a column then choose its formatting (depending on its type).  For example, for numerical values you can set the precision and choose to use scientific format, or set the font and color for negative and nonnegative values.
  • To find data using filter rules, click the "Find" button or use Tools > Find to open a Search Rules dialog box.
  • To sort the table, click the "Sort" button, use the Tools > Sort menu to open a Table Sorter dialog box in which you can select the sort columns,or just click on the column name.  Another option is to use the sortlist parameter in the browsetable() call.
  • To plot table data, click the "Plot 2D" button or use the Tools > Plot 2D menu to open a Plot Options dialog box where you can select the rows and axes to plot, along with plot display options.  Click  "Overplot" or "Clear and Plot" to make the plot in the Table Browser Plotter window.  There is also an option to export the plot; select PNG or JPG format and click Go.
  • Currently, Export > VOTable results in a Fatal IO Error and kills the table browser.
  • The default display is 1000 rows, but this can be set in the input box at the lower right.  To page through the table, use the PAGE NAVIGATION buttons to advance forward or backward one page, or go directly to the First or Last page.  You can also enter a page number and click Go.
  • To exit the table browser, use File > Exit or click the Close "X" button at the upper right of the window.

Alert: You are likely to find that browsetable needs to get a table lock before proceeding. Use the clearstat command to clear the lock status in this case.  You may also be unable to use other tasks on the table while it is open in the table browser.