fit_bkg

sherpa.astro.ui.fit_bkg(id=None, *otherids, **kwargs)

Fit a model to one or more background PHA data sets.

Fit only the backgound components of PHA data sets. This can be used to find the best-fit background parameters, which can then be frozen before fitting the data, or to ensure that these parameters are well defined before performing a simultaneous source and background fit.

Parameters:

  • id (int or str, optional) – The data set that provides the background data. If not given then all data sets with an associated background model are fit simultaneously.

  • *otherids (sequence of int or str, optional) – Other data sets to use in the calculation.

  • outfile (str, optional) – If set, then the fit results will be written to a file with this name. The file contains the per-iteration fit results.

  • clobber (bool, optional) – This flag controls whether an existing file can be overwritten (True) or if it raises an exception (False, the default setting).

Raises:

sherpa.utils.err.FitErr – If filename already exists and clobber is False.

See also

conf

Estimate the confidence intervals using the confidence method.

contour_fit

Contour the fit to a data set.

covar

Estimate the confidence intervals using the confidence method.

fit

Fit a model to one or more data sets.

freeze

Fix model parameters so they are not changed by a fit.

get_fit_results

Return the results of the last fit.

plot_fit

Plot the fit results (data, model) for a data set.

image_fit

Display the data, model, and residuals for a data set in the image viewer.

set_stat

Set the statistical method.

set_method

Change the optimization method.

set_method_opt

Change an option of the current optimization method.

set_bkg_full_model

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

set_bkg_model

Set the background model expression for a PHA data set.

set_full_model

Define the convolved model expression for a data set.

set_iter_method

Set the iterative-fitting scheme used in the fit.

set_model

Set the model expression for a data set.

show_bkg_source

Display the background model expression for a data set.

show_bkg_model

Display the background model expression used to fit a data set.

show_fit

Summarize the fit results.

thaw

Allow model parameters to be varied during a fit.

Notes

This is only for PHA data sets where the background is being modelled, rather than subtracted from the data.

Examples

Simultaneously fit all background data sets with models and then store the results in the variable fres:

>>> fit_bkg()
>>> fres = get_fit_results()

Fit the background for data sets 1 and 2, then do a simultaneous fit to the source and background data sets:

>>> fit_bkg(1,2)
>>> fit(1,2)