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#### A.4.4.9 XYArray Layer Control

The XYArray layer control () can be used to plot points, lines and error bars, but unlike the Position Layer Control it works with table cells whose values are arrays giving multiple coordinates, rather than single values. It is typically used where the value stored in each cell of a column is an array representing a whole spectrum or time series, or some related quantity (such as errors, frequencies, epochs etc). Each row of the table therefore corresponds to a full spectrum, timeseries, or other array of coordinate pairs.

You can add one of these controls to the Plane plot stack by using the Add XYArray Control () button in the control panel toolbar, or the corresponding item in the Layers menu. You may need to deactivate the default Position Layer Control stack entry () as well to avoid confusion and make sure the ranging works correctly. This control is only available for the Plane plot.

Plane Plot window with an XYArray layer

Note that unlike for instance plots of simple X,Y positions, there is no obvious single position associated with each plotted row (X/Y array pair, or wiggly line). That means that by default, you can't click on a plotted line to activate it, or see it highlighted when you activate the corresponding row by clicking on it in the Data Window. To do that, you can use the Handles Form (), which plots a "handle" marker at some configurable reference position near each line. That then serves as the effective position on the plot for each row for the purposes of activation, highlighting, graphical subset definition, etc. For convenience, a disabled Handles entry is added by default to the stack in the Forms tab, so you can enable it just by clicking on its checkbox. The handle positions and appearance can be adjusted using the configuration panel.

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.

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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