Last modified: December 2020

URL: https://cxc.cfa.harvard.edu/sherpa/ahelp/set_bkg.html
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AHELP for CIAO 4.13 Sherpa v1

set_bkg

Context: data

Synopsis

Set the background for a PHA data set.

Syntax

set_bkg(id, bkg=None, bkg_id=None)

id - int or str, optional
bkg_id - int or str, optional

Description

The background can either be fit with a model - using `set_bkg_model` - or removed from the data before fitting, using `subtract` .


Examples

Example 1

Copy the background from the default data set to data set 2:

>>> bkg1 = get_bkg()
>>> set_bkg(2, bkg1)

Example 2

Read in the PHA data from the file 'bkg.pi' and set it as the second background component of data set "core":

>>> bkg = unpack_pha('bkg.pi')
>>> set_bkg('core', bkg, bkg_id=2)

PARAMETERS

The parameters for this function are:

Parameter Definition
id The data set to use. If not given then the default identifier is used, as returned by `get_default_id` .
bkg A PHA data set, such as returned by `get_data` or `unpack_pha` .
bkg_id The identifier for this background, which is needed if there are multiple background estimates for the source.

Notes

The function does not follow the normal Python standards for parameter use, since it is designed for easy interactive use. When called with a single un-named argument, it is taken to be the `bkg` parameter. If given two un-named arguments, then they are interpreted as the `id` and `bkg` parameters, respectively. The remaining parameters are expected to be given as named arguments.

If the background has no grouping of quality arrays then they are copied from the source region. If the background has no response information (ARF or RMF) then the response is copied from the source region.


Bugs

See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.

See Also

confidence
set_conf_opt, set_covar_opt, set_proj_opt
data
get_bkg, get_bkg_arf, get_bkg_model, get_bkg_rmf, get_bkg_source, set_areascal, set_arf, set_backscal, set_coord, set_counts, set_data, set_dep, set_exposure, set_grouping, set_quality, set_rmf, set_staterror, set_syserror, subtract, unsubtract
filtering
set_filter
info
list_bkg_ids, show_bkg_model, show_bkg_source
methods
set_iter_method, set_iter_method_opt, set_method, set_method_opt
modeling
delete_bkg_model, get_par, get_xsabund, get_xscosmo, get_xsxsect, get_xsxset, set_bkg_model, set_bkg_source, set_full_model, set_model, set_par, set_pileup_model, set_source, set_xsabund, set_xscosmo, set_xsxsect, set_xsxset
plotting
plot_bkg, plot_bkg_chisqr, plot_bkg_delchi, plot_bkg_fit, plot_bkg_fit_delchi, plot_bkg_fit_resid, plot_bkg_model, plot_bkg_ratio, plot_bkg_resid, plot_bkg_source
statistics
set_prior, set_sampler, set_sampler_opt, set_stat
utilities
set_analysis, set_default_id
visualization
image_setregion