XMM-Newton Science Analysis System


selectlib (selectlib-4.78.1) [22.0.0-9173c7d25-20250127]

region-filter

region(reg.fits,x,y) is true if the point $(x,y)$ is contained in any of the regions specified in the region file reg.fits.

If the second form of the region filter region(reg.fits) is used the coordinates of the test points come from columns with names taken from the MFORM1 attribute in the specified block.

The region file may contain a column called COMPONENT. This allows shapes to be grouped together such that separate components are combined with an .OR. (i.e. points falling within any of the shapes are included) and shapes within the same component are combined with an .AND. (i.e. only points falling within all of the shapes are included). For example, a region file containing:

Shape	X	Y	R	Component
CIRCLE	25000	25000	100	1
CIRCLE	26000	25000	100	1

would give a NULL result as the two circles are from the same component and do not overlap. Whereas a file containing:

Shape	X	Y	R	Component
CIRCLE	25000	25000	100	1
CIRCLE	26000	25000	100	2

would contain all points falling within either circle.

For more informations on this and a formal definition of the region file format see Ref. [3].