09.2. How to add a column to the results table

RSP Aspect: Portal

Contact authors: Greg Madejski and Melissa Graham

Last verified to run: 2025-02-04

Targeted learning level: beginner

Introduction: This tutorial demonstrates how to derived new columns from retrieved columns in the Portal results tab.

1. Execute a query. Go to the Portal’s DP0.2 Catalogs tab, switch to the ADQL interface, and execute the query below. This query will retrieve a small sample of point-like objects (stars) brighter than 25th magnitude (as in preceding tutorials).

SELECT coord_dec, coord_ra, detect_isPrimary, refExtendedness,
       u_cModelFlux, g_cModelFlux, r_cModelFlux,
       i_cModelFlux, z_cModelFlux, y_cModelFlux
FROM dp02_dc2_catalogs.Object
WHERE CONTAINS(POINT('ICRS', coord_ra, coord_dec),
      CIRCLE('ICRS', 62, -37, 0.167)) =1
      AND (detect_isPrimary =1 AND refExtendedness =1
           AND u_cModelFlux >360 AND g_cModelFlux >360
           AND r_cModelFlux >360 AND i_cModelFlux >360
           AND z_cModelFlux >360 AND y_cModelFlux >360)

2. View the default table (Figure 1). Only one query has been executed, so there is only one tab in the table panel (A in Figure 1).

The default view of the table panel.

Figure 1: The table panel that results from the query in step 1. The third row has been clicked on and is highlighted orange.

3. Open the “Add a column” window. Click on the “add column” icon (H in Figure 1) to open the pop-up window in Figure 2.

The pop-up window to add a new column, with entry field boxes to define the derived column.

Figure 2: The pop-up window to add a new column, with entry field boxes set to define a new derived column of g-band AB magnitudes.

4. Define the new column. New columns can only be derived from pre-existing columns using an expression. In the pop-up window, name the new column g_cModelMag. Use the following expression, which converts fluxes (in units of nJy) into AB magnitudes: -2.5 * LOG10(g_cModelFlux) + 31.4. Provide the units of the new column as mag, and add a description. Click “Add Column”, and it will appear in the table.

5. Option to save the table. Click on the save icon (G in Figure 1), choose a file format of comma-separated values (CSV) and name the file as “my_table.csv”. Leave the default selection of “Save table as displayed” in order to include the new derived column of g-band magnitudes, and click “Save” to download the file.

The pop-up window to save a table.

Figure 3: The pop-up window to save a table, with the selections as described in step 5.

Return to the list of DP0.2 Portal tutorials.