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#### A.5.5.2 Size Form

Size form configuration panel

The Size form () plots markers of a fixed shape whose size varies according to a supplied data coordinate. The marker size thus represents an additional dimension of the plot.

The marker size is scaled according to the values of the data. The data range in the visible part of the plot is determined, the maximum value is assigned to the maximum marker size, and the size of each marker is determined as (data value)/(max data value). Currently data values of zero always correspond to marker size of zero, negative data values are not represented, and the mapping is linear. Other options may be introduced in future.

Note the scaling to size is in terms of screen dimensions (pixels). For sizes that correspond to actual data values, the Error form may be more appropriate.

The configuration options are:

Shading Mode
  See Appendix A.5.6.
Size
  The size coordinate data values. Fill this in with a column name or expression from the table just like for the positional coordinates.
Shape
  Marker shape from a list of options.
Max Marker Size
  Scales the maximum marker size in pixels. Slide this along to scale the sizes of all the markers up or down.

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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