Available Functions Window
This window displays all the functions (Java methods) which are
available for use when writing
algebraic expressions.
This includes both the built-in expressions and any
extended ones you might have added.
You can find this window by using the
Show Functions () button in the
Synthetic Column or
Algebraic Subset
window toolbars.
On the left hand side of the window is a tree-like representation of the functions you can use. Each item in this tree is one of the following:
Of these, the Folder and Class items have a 'handle' (),
which means that they contain other items
(classes and functions/constants respectively).
By clicking on the handle (or equivalently double-clicking on the name)
you can toggle whether the item is open (so you can see its contents)
or closed (so you can't). So to see the functions in a class,
click on its handle and they will be revealed.
You can click on any of these items and information about it
will appear in the right hand panel. In the case of functions
this describes the function, its arguments, what it does, and
how to use it. The explanations should be fairly self-explanatory;
for instance the description in the figure above indicates that
you could use the invocation atan2(X_POS,Y_POS)
as the expression for a new table column which gives the angle from
the X axis of a point whose position is given by columns with
the names X_POS and Y_POS.
Examples of a number of these functions are given in
Section 6.7.
Using the Add button ()
you can specify the name of a class to add to those available.
You should enter the fully-qualified class name (i.e. including the
dot-separated package path). The class that you specify must be
on the class path which was current when TOPCAT was started,
as explained in Section 9.2.1.
Note however it would be more usual to specify these using
the system property
jel.classes
or
jel.classes.activation
at startup,
as described in Section 6.8.
Classes added in this way will be visible in the tree, but may
not have proper documentation (clicking on them may not reveal
a description in the right hand panel).