Dynamically linked data displays

In Descartes it is possible to build multiple displays representing different attributes of the same data set or, possibly, the same attributes in different ways. Thus, the user can open one or more maps and various kinds of non-cartographic displays: dot plots, scatter plots, parallel coordinate plots. All these displays are dynamically linked. Thus, when the user points with the mouse on an object in one of the displays, the graphical elements corresponding to this object (contour in a map, dot in a dot plot or a scatter plot, line in a parallel coordinate plot) are simultaneously highlighted in all the displays.

The Descartes system supports two kinds of highlighting: transient and durable. Transient ("mouse-over") highlighting occurs when the mouse cursor is positioned over an object and is switched off immediately after the mouse is moved aside. Durable highlighting occurs when an object is selected by clicking or dragging the mouse and lasts until the user explicitly cancels it. Click on a durably highlighted object cancels its highlighting. Click in an object-free area of any display cancels highlighting of all objects. Descartes uses white color for transient highlighting and black for durable highlighting.

Important notes:

Selection of objects to be durably highlighted by mouse clicking is automatically enabled. However, a user may wish that some map manipulator, such as the visual comparison tool, react to mouse clicking events. When the user selects this option, the manipulator captures the mouse click events, and they are no more used for highlighting. The user can explicitly switch the interpretation of mouse click events back to highlighting using the appropriate controls in the manipulator area.
Selection by mouse dragging is automatically enabled in all non-cartographic displays. In a map window mouse dragging can be used as well for zooming and shifting of the viewport. The user can switch between different interpretations of mouse dragging using button switches in the tool bar of the map window.
In a map with several layers only objects of the active layer can be affected by highlighting. To make a layer active, the user should click on it in the legend. When the active layer changes, highlighting of objects from the previously active layer is cancelled. It will appear again when this layer is activated once more.

For example, having on the screen a map and a scatter plot, an analyst can highlight dots in the scatter plot she finds interesting and look on the map where the corresponding objects are located. She can also select objects in the map and analyze their positions among other objects in the scatter plot.

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