Module functions for setting source and background extraction region areas.
Integer_Type set_backscale([Integer_Type],Float_Type)
Integer_Type set_bbackscale([Integer_Type],Float_Type)
Success/Error Return Values: 1/0
Arguments:
(1) Dataset number (default 1)
(2) Extraction region area
These functions take their names from the PHA header keyword
BACKSCAL. BACKSCAL can be defined as the
ratio of the area of the source (or background) extraction region in
image pixels to the total number of image pixels. The fact that there
is no ironclad definition for this quantity does not matter so long
as the BACKSCAL for a source dataset and its associated
background dataset are defined in the similar manner, because only the
ratio of source and background BACKSCAL is used in
analyses.
The specified backscale replaces the current value of the backscale
within Sherpa, which as mentioned above may have been set
when the dataset was loaded from the value of
the BACKSCAL header keyword of a PHA file.
See the related Sherpa commands
SETDATA and
SETBACK for more information.
Change the backscale value of dataset 1 from 0.0441895 to 0.07:
sherpa> get_backscale()
0.0441895
sherpa> set_backscale(1,0.07)
1
sherpa> get_backscale()
0.07
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