- ←Prev
- AST
A Library for Handling
World Coordinate Systems
in Astronomy - Next→
- TOC ↑
Description:
This
function 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
astGrid function).
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 non-linear. Any discontinuities in the
Mapping between physical and graphical coordinates are catered for, as is any
clipping established using astClip.
Synopsis
void astGridLine( AstPlot
this,
int axis, const double start[], double length )
Parameters:
this
Pointer to the
Plot.
axis
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
An array, with one element for each axis of the Plot, giving the physical
coordinates of the start of the curve.
length
The length of curve to be drawn,
given as an increment along the selected physical axis. This may be positive or
negative.
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 2-dimensional.
-
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) 2021 East Asian Observatory
- ←Prev
- AST
A Library for Handling
World
Coordinate Systems
in Astronomy - Next→
- TOC ↑