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## 3 Apparent Table

The Apparent Table is a particular view of a table which can be influenced by some of the viewing controls.

When you load a table into TOPCAT it has a number of characteristics like the number of columns and rows it contains, the order of the rows that make up the data, the data and metadata themselves, and so on. While manipulating it you can modify the way that the table appears to the program, by changing or adding data or metadata, or changing the order or selection of columns or rows that are visible. For each table its "apparent table" is a table which corresponds to the current state of the table according to the changes that you have made.

In detail, the apparent table consists of the table as it was originally imported into the program plus any of the following changes that you have made:

- Selection of rows changed by changing the current Row Subset
- Changes to the current Row Order caused by doing a sort
- Changes to the current Column Set caused by adding, hiding or moving columns
- Changes to cell data by editing cells in the Data window
- Changes to table metadata by editing cells in the Parameter window
- Changes to column metadata by editing cells in the Columns window

The apparent table is used in the following contexts:

Data Window
  The Data window always shows the rows and columns of the apparent table, so if you are in doubt about what form a table will get exported in, you can see what it looks like there.
Exports
  When you save a table, or export it by dragging it off the Table List panel in the Control Window, or create a duplicate table, it is the apparent table which is copied. So for instance if you define a subset containing only the first ten rows of a table and then save it to a new table, or create a duplicate within TOPCAT using the Duplicate Table () toolbar button, the resulting table will contain only those ten rows.
Joins
  When you use the Match Window or Concatenation Window to construct a new table on the basis of one or more existing ones, the new table will be built on the basis of the apparent versions of the tables being operated on. The same applies to the join-like functionality provided by table uploads in the TAP window, CDS Upload X-Match window and the multiple positional search (Cone, SIA, SSA) windows.

Some of the other table view windows are affected too, for instance the Columns window displays its columns in the order that they appear in the Apparent Table.

- 3.1 Row Subsets

- 3.1.1 Defining Subsets

- 3.2 Row Order
- 3.3 Column Set

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk