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The Aux Axis control (
) is only
visible when the Aux colour mode
has been selected for one of the data layers;
if no layer is using Aux shading, the control will not appear in the stack.
It controls a single colour scale for points which
are coloured by data value to represent an additional dimension in the data.
When present, this control has three following tabs.
Aux axis control Map tab
The Map tab controls the aux axis colour map.
It has the following options:
-
Aux Shader
- Select the colour map from a list of options.
-
Shader Clip
- Select a sub-range of the full colour map above.
By default the whole colour map is used, but if you want the range
of colours in the plot to be formed from only a part of the colour
band shown in the Shader control,
you can move the handles in from the end of this slider.
-
Shader Flip
- Whether the aux scale should map forwards or backwards
into the colour map.
-
Shader Quantise
- Allows the colour map to be quantised.
By default, the colour map is effectively continuous.
If you slide the slider to the right, the map will be split into
a decreasing number of discrete colours. This can be used to generate
a contour-like efect, and may make it easier to trace the boundaries
of regions of interest by eye.
-
Scaling
- Determines the function used to map the range of aux data values
onto the colour map.
Options are linear,
logarithmic,
square and
square root.
-
Null Colour
- What colour should be used to represent points with a null value
for the aux data coordinate.
If the associated Hide option is selected,
then those points will not appear in the plot at all.
Aux axis control Ramp tab
The Ramp tab controls the display and annotation of
the colour ramp that displays the colour map on the plot.
It has the following options:
-
Show Scale
- Whether the aux scale ramp is visible;
if so an appropriately labelled colour ramp
appears at the right of the plot.
The associated Auto option makes this decision
automatically: if any aux data is plotted, the scale will appear,
otherwise it won't.
Deselect Auto if you want to determine visibility by hand.
-
Aux Axis Label
- Selects the axis label to be displayed near the aux colour ramp
if it is visible.
The associated Auto option, if selected, uses the
name of one of the coordinates supplying aux data;
deselect Auto if you want to enter a label by hand.
-
Aux Tick Crowding
- The slider influences how many tick marks are drawn on the colour ramp.
Aux axis control Range tab
The Range tab lets you enter lower and upper values
for the aux data range by hand,
and provides a double slider to restrict the range within these limits.
If either the lower or upper range is left blank,
it will be determined from the data.
Note the font used for labelling the aux axis is currently controlled by
the font from the Axes selector.
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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