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A Library for Handling
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Description:
This routine draws a curve in
the physical coordinate system of a
Plot by varying only one of the coordinates along the length of
the curve. It is intended for drawing coordinate axes, coordinate grids, and tick marks
on axes (but note that these are also available via the more comprehensive
AST_GRID
routine).
The curve is transformed into graphical coordinate space for plotting, so that a straight line in physical
coordinates may result in a curved line being drawn if the Mapping involved is nonlinear. Any
discontinuities in the Mapping between physical and graphical coordinates are catered for, as is any
clipping established using AST_CLIP.
Invocation
CALL AST_GRIDLINE( THIS, AXIS,
START, LENGTH, STATUS )
Arguments
THIS = INTEGER (Given)
Pointer to the Plot.
AXIS = INTEGER (Given)
The index of the Plot axis whose physical coordinate value is
to be varied along the length of the curve (all other coordinates will remain fixed). This
value should lie in the range from 1 to the number of Plot axes (
Naxes attribute).
START(
$\ast $ ) =
DOUBLE PRECISION (Given)
An array, with one element for each axis of the Plot, giving the
physical coordinates of the start of the curve.
LENGTH = DOUBLE PRECISION (Given)
The length
of curve to be drawn, given as an increment along the selected physical axis. This may be positive
or negative.
STATUS = INTEGER (Given and Returned)
The global status.
Notes:

No curve is drawn if the START array contains any coordinates with the value AST__BAD, nor if
LENGTH has this value.

An error results if the base Frame of the Plot is not 2dimensional.

An error also results if the transformation between the current and base Frames of the Plot is not
defined (i.e. the Plot’
s TranInverse attribute is zero).
Copyright (C) 2017 East Asian Observatory
 ←Prev
 AST
A Library for Handling
World Coordinate
Systems
in Astronomy  Next→
 TOC ↑