get_bkg_scale

sherpa.astro.ui.get_bkg_scale(id=None)

Return the background scaling factor for a PHA data set.

Return the factor applied to the background component to scale it to match it to the source (either when subtracting the background, or fitting it simultaneously).

Parameters

id (int or str, optional) – The identifier for the data set to use. If not given then the default identifier is used, as returned by get_default_id.

Returns

ratio – The scaling factor. The result can vary per channel, in which case an array is returned.

Return type

number or array

See also

get_areascal()

Return the fractional area factor of a PHA data set.

get_backscal()

Return the area scaling factor for a PHA data set.

set_backscal()

Change the area scaling of a PHA data set.

set_full_model()

Define the convolved model expression for a data set.

set_bkg_full_model()

Define the convolved background model expression for a PHA data set.

Notes

The scale factor:

exp_src * bscale_src / (exp_bgnd * bscale_bgnd)

where exp_x and bscale_x are the exposure and BACKSCAL values for the source (x=src) and background (x=bgnd) regions, respectively.

Examples

>>> get_bkg_scale('pi')
0.034514770047217924