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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
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