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#### A.4.4.3 Quad Position Layer Control

The Quad Position layer control () allows you to plot symbols defined by four positions in the plot space from each row of a table - typically some kind of quadrilateral. You can add one of these controls to the stack by using the Add Quad Control () button in the control panel toolbar, or the corresponding item in the Layers menu.

It works like the Single Position and Pair Position Layer Controls, but the Position tab has fields for four sets of coordinates to fill in.

Sky Plot Window with a Quad control

This control is a Table Data control as described in Appendix A.4.2.2. That section explains the Subsets tab; the Position and Form tabs are described in more detail below.

If you want to draw triangles instead of quadrilaterals, you can just supply the same coordinates for two of the positions. If you want a polygon with more vertices, try the Polygon form from the single position layer control.

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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@jiscmail.ac.uk