Synopsis
Calculate the Chi Squared statistic contribution per bin
Syntax
calc_chisqr( [ id, [otherids]] )
Description
When fitting data with Chi Squared statistics, the calc_chisqr function returns an array of Chi Squared statistic contributions for each bin of the specified data set ID(s). The data set ID(s) supplied to calc_chisqr must be ready for fitting, i.e. it has been assigned a model to be fit. The calc_chisqr function can be called with no arguments, in which case the Chi Squared statistic array for the first data set ready for fitting will be returned. If multiple data set IDs are given, then the simultaneous Chi Squared fit statistics are calculated for those data sets.
- id, otherids - the id(s) of the dataset(s) to use; if not given, uses the default dataset id (id=1 by default, see "ahelp get_default_id"); otherids=None
Below are the Chi Squared fit statistics available in Sherpa:
chi2constvar | chi^2 with constant variance computed from the counts data. |
---|---|
chi2modvar | chi^2 with model amplitude variance. |
chi2gehrels | chi^2 with gehrels method (default). |
chi2datavar | chi^2 with data variance. |
chi2xspecvar | chi^2 with data variance (XSPEC-style, variance = 1.0 if data less than or equal to 0.0) |
Examples
Example 1
sherpa> calc_chisqr()
When called with no arguments, calc_chisqr() returns the Chi Squared statistic array for the default data set, if it has been assigned a model to be fit.
Example 2
sherpa> calc_chisqr(1) sherpa> calc_chisqr("src")
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.
Example 3
sherpa> calc_chisqr(1,2) sherpa> calc_chisqr("src", "bkg")
When supplied with multiple data set IDs, calc_chisqr returns the Chi Squared statistic array produced by the simultaneous fit on those 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_plot
- fitting
- fit
- 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_order_plot, get_par, get_pileup_model, get_source, get_source_component_image, get_source_component_plot, image_model, image_model_component, image_source, image_source_component, integrate, integrate1d, link, load_table_model, load_template_model, load_user_model, normal_sample, reset, save_model, save_source, set_bkg_model, set_full_model, set_model_autoassign_func, set_pileup_model, set_source, set_xsabund, set_xscosmo, set_xsxsect, set_xsxset, t_sample, uniform_sample
- plotting
- get_lrt_plot, get_lrt_results, get_pvalue_plot, get_pvalue_results, plot_cdf, plot_fit, 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
- 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, get_ratio, get_resid, image_fit