Include a spatial region of all data sets.
Select a spatial region to include in the fit. The filter is applied to all data sets.
val (str, optional) – A region specification as a string or the name of a file containing a region filter. The coordinates system of the filter is taken from the coordinate setting of the data sets (set_coord). If
None, then all points are included.
The region syntax support is provided by the CIAO region library 1, and supports the following shapes (the capitalized parts of the name indicate the minimum length of the name that is supported):
Angles are measured in degrees from the X axis, with a positive value indicating a counter-clockwise direction.
Only simple polygons are supported, which means that a polygon can not intersect itself. The last point does not need to equal the first point (i.e. polygons are automatically closed if necessary).
The shapes can be combined using AND (intersection), OR (union), or NOT (negation):
shape1()+shape2() shape1()|shape2() shape1()shape2()
!shape1() shape1()-shape2() shape1()*!shape1()
The precedence uses the same rules as the mathematical operators
*!), so that:
means that the second circle is only excluded from the rectangle, and not the first circle. To remove it from both shapes requires writing:
A point is included if the center of the pixel lies within the region. The comparison is done using the selected coordinate system for the image, so a pixel may not have a width and height of 1.
Include the data points that lie within a circle centered at 4324.5,3827.5 with a radius of 300:
Read in the filter from the file
ds9.reg, using either:
Select those points that lie both within the rotated box and the annulus (i.e. an intersection of the two shapes):
Select those points that lie within the rotated box or the annulus (i.e. a union of the two shapes):
All existing spatial filters are removed: