Defining New Components

New components of data items can be easily created from mathematical operations on existing components. In this section, we define new components for the W5 Point Source catalog from the tutorial.

Right-click on the w5_psc item in the Data Collection window and select Define new component:

../_images/define_component_01.png

A new window will appear for defining components. Double-clicking on any of the Available Components will add it to the expression line. You can also type the name of the component – it will appear in blue if it is valid and in red if not, when separated by spaces from other parts of the expression. Here we define a new component __24__-__3.6_ to be the difference between 24 micron and 3.6 micron magnitudes:

../_images/define_component_02.png

Remember to select the data item on the Add to window (here, w5_psc).

After clicking OK, the new component is available for plotting and other uses.

Furthermore, the expression line can include Numpy functions (prefaced with np.), and anything else you import in your config.py file for Glue. For example, if you wished to define a component expressing the 24 micron flux density in Janskys, you could use the np.power function:

../_images/define_component_numpy.png