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Description:
This
attribute is a boolean value which suggests how the axes of a
Frame should
be displayed (e.g.) in graphical output. By default, it has the value one,
indicating that they should be shown in the conventional sense (increasing
left to right for an abscissa, and bottom to top for an ordinate). If set to
zero, this attribute indicates that the direction should be reversed, as would
often be done for an astronomical magnitude or a right ascension axis.
Type:
Integer (boolean). Applicability
Frame
The default Direction value supplied
by the Frame class is 1, indicating that all axes should be displayed in the
conventional direction.
The SkyFrame class re-defines the default
Direction value to suggest that certain axes (e.g. right ascension) should be
plotted in reverse when appropriate.
The Direction attribute
of a FrameSet axis is the same as that of its current Frame (as specified by
the
Current attribute).
The Direction attribute of the base Frame
in a Plot is set to indicate the sense of the two graphics axes, as implied
by the graphics bounding box supplied when the Plot was created.
Notes:
-
When specifying this attribute by name, it should be subscripted with the number of the
Frame axis to which it applies.
-
The Direction attribute does not directly affect the behaviour of the AST library.
Instead, it serves as a hint to applications programs about the orientation in which
they may wish to display any data associated with the Frame. Applications are free to
ignore this hint if they wish.
Copyright (C) 2021 East Asian Observatory
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- AST
A Library for Handling
World
Coordinate Systems
in Astronomy - Next→
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