When each table is imported it has a list of columns. Each column has header information which determines the kind of data which can fill the cells of that column as well as a name, and maybe some additional information like units and Unified Content Descriptor. All this information can be viewed, and in some cases modified, in the Columns Window.
During the lifetime of the table within TOPCAT, this list of columns can be changed by adding new columns, hiding (and perhaps subsequently revealing) existing columns, and changing their order. The current state of which columns are present and visible and what order they are in is collectively known as the Column Set, and affects the Apparent Table. The current Column Set is always reflected in the order in which columns are displayed in the Data Window and Statistics Window. The Columns Window shows all the known columns, including hidden ones, in Column Set order; whether they are currently visible is indicated by the (leftmost) "Visible" column.
You can affect the current Column Set in the following ways:
) or
Reveal Selected (
)
button in the toolbar or menu.
Note when selecting rows, don't drag the mouse over the Visible
column, do it somewhere in the middle of the table.
The Hide All (
) and
Reveal All (
)
buttons set all columns in the table invisible or visible -
a useful convenience if you've got a very wide table.
You can also hide a column by right-clicking on it in the Data Window, which brings up a popup menu - select the Hide option. To make it visible again you have to go to the Columns Window as above.
)
or New Sky Coordinate Columns (
) buttons in the
Columns Window or the (right-click) popup menu in the
Data Window to add new columns derived from exsiting ones.
) button.
This is similar to the Add a Synthetic Column
described in the previous item, but it pops up a new column
dialogue with similar characteristics (name, units etc)
to those of the column that's being replaced, and when completed
it slots the new column in to the table hiding the old one.
) button, which will add
a new boolean column to the table with the value true
for rows part of that subset and false for the other rows.