Define the convolved background model expression for a PHA data set.
set_bkg_full_model(id, model=None, bkg_id=None) id - int or str, optional model - str or sherpa.models.Model object bkg_id - int or str, optional
Set a model expression for a background data set in the same way that `set_full_model` does for a source. This is for when the background is being fitted simultaneously to the source, rather than subtracted from it.
The background is fit by two power laws - one that is passed through the instrument response ( gbgnd ) and one that is not ( pbgnd ). The source is modelled by xsphabs * galabs , together with the background model, scaled by the ratio of area and time. Note that the background component in the source expression uses the source response rather than background response.
>>> rsp = get_response() >>> bresp = get_response(bkg_id=1) >>> bscale = get_bkg_scale() >>> smodel = xsphabs.galabs * xsapec.emiss >>> bmdl = brsp(powlaw1d.gbdng) + powlaw1d.pbgnd >>> smdl = rsp(smodel) + bscale*(rsp(gbgnd) + pbgnd) >>> set_full_model(smdl) >>> set_bkg_full_model(bmdl)
The parameters for this function are:
|id||The data set containing the source expression. If not given then the default identifier is used, as returned by `get_default_id` .|
|model||This defines the model used to fit the data. It can be a Python expression or a string version of it.|
|bkg_id||The identifier for the background of the data set, in cases where multiple backgrounds are provided.|
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 `model` parameter. If given two un-named arguments, then they are interpreted as the `id` and `model` parameters, respectively.
Some functions - such as `plot_bkg_source` - may not work for model expressions created by `set_bkg_full_model` .
See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.