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### A.5.1 Differences From Classic Plot Windows

A brief summary of improvements these windows offer over the classic plot windows is:

New Sky Coordinate Plot
  - Choice of projection: Sin (rotatable), Aitoff, Plate Carrée
  - Data and view sky coordinate systems selected separately: options are equatorial, galactic, supergalactic, ecliptic
  - Sky coordinate grid labelled and visible at all zooms
New data plot options
  - vectors
  - ellipses (with position angle)
  - pair, triple, ... data point lines/polygons
  - contours
  - variable size markers
Improved interactive response
  - In 2d and sky plots mouse wheel zooms around cursor position
  - In 2d and sky plots you can drag the plot around
  - In 3d plots right mouse button recentres cube on selected point
  - In 3d plots zooming zooms data in the cube rather than enlarging the cube wireframe itself
  - Many controls are sliders which update the plot as you slide
Better support for large datasets
  Several features have been introduced to provide more meaningful visualisation of large datasets. Improved density-like plots and contours give you better ways to understand plots containing many more points than there are pixels to plot them on. There is separately some improvement in scalability: up to roughly 10 million points is currently feasible depending on available memory etc, though it depends what you're doing. However, I hope to improve this limit in future.
New plot shading modes
  Density colour coding for all plot types, with colour map either absolute or modifying dataset base colour. Flat, transparent and aux colour coding still available as before.
Improved axis labelling
  - Choice of font size and style
  - Option of LaTeX input for non-ASCII characters etc
  - Log axes labelled better
  - Minor tick option
Legend options
  External or manually positioned internal placement.
Analytic function plotting in 2D
  Plot functions of X or Y coordinate using TOPCAT expression language.

The new windows allow you to assemble a stack of layers representing different plot types of different data sets on the same axes. The user interface for controlling this is quite a bit different than for the classic plot windows, and is described in the subsequent sections. However, making a simple plot is still simple: select a table, select the columns, and you're off.

Some features not currently available in the layer plots include the 1-d histogram, the stacked line plot, and true RGB density maps (though density shading modes will often do as good or a better job). The intention is to introduce these in a future release.

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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