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### A.4.1 Differences From Old-Style Plot Windows

A brief summary of improvements these windows offer over the old-style 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, configurable and visible at all zooms
New data plot options
  - Vectors
  - Ellipses (with position angle)
  - Pair data point links
  - Contours
  - Variable size markers
  - Kernel density estimates
  - ... and many more
Improved interactive response
  - Various mouse wheel and drag actions pan and zoom the plot instantly
  - 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: you can typically get reasonable interactive performance up to about 10 million points depending on available memory etc and what you're doing (though there are reports of it working with several 108 points). The intention is to improve this limit further in future.
New plot shading modes
  Density colour coding for all plot types, with colour map either absolute or modifying dataset base colour. The result is something that looks like a scatter plot at low densities and a density plot for high densities, and generally means that you can easily make quantitative sense of overcrowded regions of a scatter plot. 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
Analytic function plotting in 2D
  Plot functions of X or Y coordinate using algebraic expression language.
Configurability
  Many more configuration options including legend placement, grid display and colour, antialiasing, text label crowding limits etc etc.
STILTS export
  The GUI can report the text for the STILTS command that would reproduce the currently visible plot.

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 old-style 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 from the old-style plots that are not currently available in the new-style plots are:

- true RGB density maps (though density shading modes will often do as good or a better job)
- fogging in 3D plots

These may be introduced in a future release, possibly informed by user demand.

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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