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8.4.5 density

Paints markers using a configurable colour map to indicate how many points are plotted over each other. Specifically, it colours each pixel according to how many times that pixel has has been covered by one of the markers plotted by the layer in question. To put it another way, it generates a false-colour density map with pixel granularity using a smoothing kernel of the form of the markers plotted by the layer. The upshot is that you can see the plot density of points or other markers plotted.

This is like auto mode, but with more user-configurable options.

Usage:

   shadingN=density colorN=<rrggbb>|red|blue|...
                    densemapN=scale_v|pastel|rainbow|... denseclipN=<lo>,<hi>
                    denselogN=true|false denseflipN=true|false
                    densesubN=<lo>,<hi>

All the parameters listed here affect only the relevant layer, identified by the suffix N.

Associated parameters are as follows:

colorN = <rrggbb>|red|blue|...       (Color)
The color of plotted data.

The value may be a six-digit hexadecimal number giving red, green and blue intensities, e.g. "ff00ff" for magenta. Alternatively it may be the name of one of the pre-defined colors. These are currently red, blue, green, grey, magenta, cyan, orange, pink, yellow, black, white.

[Default: ff0000]

denseclipN = <lo>,<hi>       (Subrange)
Defines a subrange of the colour ramp to be used for Density shading. The is specified as a (low,high) comma-separated pair of two numbers between 0 and 1.

If the full range 0,1 (the default) is used, the whole range of colours specified by the selected shader will be used. But if, for instance a value of 0,0.5 is given, only those colours at the left hand end of the ramp will be seen.

[Default: 0,1]

denseflipN = true|false       (Boolean)
If true, the sense of the scale used for shading points according to density is reversed (the colour ramp is flipped).

[Default: false]

denselogN = true|false       (Boolean)
If true, the scale used for shading points according to density is logarithmic, if false, it's linear.

[Default: true]

densemapN = scale_v|pastel|rainbow|...       (Shader)
Color map used to indicate point density.

A mixed bag of colour ramps are available: scale_v, pastel, rainbow, rainbow2, accent, gnuplot, gnuplot2, cubehelix, specxby, cyan-magenta, red-blue, heat, cold, light, greyscale, scale_v, scale_s, colour, standard, bugn, bupu, orrd, pubu, purd. Note: many of these, including rainbow-like ones, are frowned upon by the visualisation community.

[Default: scale_v]

densesubN = <lo>,<hi>       (Subrange)
Defines a normalised adjustment to the data range of the Density axis. The value may be specified as a comma-separated pair of two numbers, giving the lower and upper bounds of the range of of interest respectively. This sub-range is applied to the data range that would otherwise be used, either automatically calculated or explicitly supplied; zero corresponds to the lower bound and one to the upper.

The default value "0,1" therefore has no effect. The range could be restricted to its lower half with the value 0,0.5.

[Default: 0,1]


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STILTS - Starlink Tables Infrastructure Library Tool Set
Starlink User Note256
STILTS web page: http://www.starlink.ac.uk/stilts/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk