Last modified: December 2020

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

calc_chisqr

Context: utilities

Synopsis

Calculate the per-bin chi-squared statistic.

Syntax

calc_chisqr(id=None, *otherids)

id - int or str, optional
*otherids - int or str, optional

Description

Evaluate the model for one or more data sets, compare it to the data using the current statistic, and return an array of chi-squared values for each bin. No fitting is done, as the current model parameter, and any filters, are used.


Examples

Example 1

When called with no arguments, the return value is the chi-squared statistic for each bin in the data sets which have a defined model.

>>> calc_chisqr()

Example 2

Supplying a specific data set ID to calc_chisqr - such as "1" or "src" - will return the chi-squared statistic array for only that data set.

>>> calc_chisqr(1)
>>> calc_chisqr("src")

Example 3

Restrict the calculation to just datasets 1 and 3:

>>> calc_chisqr(1, 3)

PARAMETERS

The parameters for this function are:

Parameter Definition
id The data set that provides the data. If not given then all data sets with an associated model are used simultaneously.
*otherids Other data sets to use in the calculation.

Return value

The return value from this function is:

chisq -- The chi-square value for each bin of the data, using the current statistic (as set by `set_stat` ). A value of none is returned if the statistic is not a chi-square distribution.

Notes

The output array length equals the sum of the arrays lengths of the requested data sets.


Bugs

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

See Also

data
get_bkg_chisqr_plot, get_bkg_delchi_plot, get_bkg_fit_plot, get_bkg_model_plot, get_bkg_plot, get_bkg_ratio_plot, get_bkg_resid_plot, get_bkg_source_plot
fitting
fit, simulfit
info
list_model_ids, show_bkg_model, show_bkg_source
methods
get_iter_method_name, get_iter_method_opt, list_iter_methods, set_iter_method, set_iter_method_opt
modeling
add_model, add_user_pars, clean, create_model_component, delete_bkg_model, delete_model, delete_model_component, get_model, get_model_autoassign_func, get_model_component, get_model_component_image, get_model_component_plot, get_model_plot, get_num_par, get_num_par_frozen, get_num_par_thawed, get_order_plot, get_par, get_pileup_model, get_source, get_source_component_image, get_source_component_plot, get_source_contour, get_source_image, get_source_plot, get_xsabund, get_xscosmo, get_xsxsect, get_xsxset, image_model, image_model_component, image_source, image_source_component, integrate, link, load_table_model, load_template_interpolator, load_template_model, load_user_model, normal_sample, reset, save_model, save_source, set_bkg_model, set_bkg_source, set_full_model, set_model, set_model_autoassign_func, set_pileup_model, set_source, set_xsabund, set_xscosmo, set_xsxsect, set_xsxset, t_sample, uniform_sample
plotting
get_cdf_plot, get_pdf_plot, get_pvalue_plot, get_pvalue_results, plot_cdf, plot_fit, plot_fit_delchi, plot_fit_resid, plot_model, plot_model_component, plot_pdf, plot_pvalue, plot_scatter, plot_source, plot_source_component, plot_trace
psfs
delete_psf, load_conv
saving
save_delchi, save_resid
statistics
get_stat, get_stat_name
tools
aprates, modelflux
utilities
calc_energy_flux, calc_model_sum, calc_photon_flux, calc_source_sum, calc_stat, eqwidth, gamma, igam, igamc, incbet, lgam
visualization
contour_model, contour_ratio, contour_resid, image_fit