Last modified: December 2023

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AHELP for CIAO 4.16 Sherpa


Context: data


Return the statistical error on the dependent axis of a data set.


get_staterror(id=None, filter=False, bkg_id=None)

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


The function returns the statistical errors on the values (dependenent axis) of a data set, or its background. These may have been set explicitly - either when the data set was created or with a call to `set_staterror` - or as defined by the chosen fit statistic (such as "chi2gehrels").


Example 1

If not explicitly given, the statistical errors on a data set may be calculated from the data values (the independent axis), depending on the chosen statistic:

>>> load_arrays(1, [10, 15, 19], [4, 5, 9])
>>> set_stat('chi2datavar')
>>> get_staterror()
array([ 2.        ,  2.23606798,  3.        ])
>>> set_stat('chi2gehrels')
>>> get_staterror()
array([ 3.17944947,  3.39791576,  4.122499  ])

Example 2

If the statistical errors are set - either when the data set is created or with a call to `set_staterror` - then these values will be used, no matter the statistic:

>>> load_arrays(1, [10, 15, 19], [4, 5, 9], [2, 3, 5])
>>> set_stat('chi2datavar')
>>> get_staterror()
array([2, 3, 5])
>>> set_stat('chi2gehrels')
>>> get_staterror()
array([2, 3, 5])


The parameters for this function are:

Parameter Definition
id The identifier for the data set to use. If not given then the default identifier is used, as returned by `get_default_id` .
filter Should the filter attached to the data set be applied to the return value or not. The default is False .
bkg_id Set if the values returned should be from the given background component, instead of the source data set.

Return value

The return value from this function is:

staterrors -- The statistical error for each data point. This may be estimated from the data (e.g. with the chi2gehrels statistic) or have been set explicitly ( `set_staterror` ). For PHA data sets, the return array will match the grouping scheme applied to the data set. The size of this array depends on the `filter` argument.


The default behavior is to not apply any filter defined on the independent axes to the results, so that the return value is for all points (or bins) in the data set. Set the `filter` argument to `True` to apply this filter.


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

See Also

get_conf, get_conf_results, get_covar, get_covar_opt, get_covar_results, get_covariance_results, get_int_proj, get_int_unc, get_proj, get_proj_opt, get_proj_results, get_projection_results, get_reg_proj, get_reg_unc
get_chart_spectrum, get_marx_spectrum
copy_data, dataspace1d, dataspace2d, datastack, delete_data, fake, get_areascal, get_arf, get_arf_plot, get_axes, get_backscal, get_bkg, get_bkg_arf, get_bkg_chisqr_plot, get_bkg_delchi_plot, get_bkg_fit_plot, get_bkg_model, get_bkg_model_plot, get_bkg_plot, get_bkg_ratio_plot, get_bkg_resid_plot, get_bkg_rmf, get_bkg_scale, get_bkg_source, get_bkg_source_plot, get_coord, get_counts, get_data, get_data_contour, get_data_contour_prefs, get_data_image, get_data_plot, get_data_plot_prefs, get_dep, get_dims, get_error, get_exposure, get_grouping, get_indep, get_quality, get_rmf, get_specresp, get_syserror, group, group_adapt, group_adapt_snr, group_bins, group_counts, group_snr, group_width, load_ascii, load_data, load_grouping, load_quality, set_data, set_quality, ungroup, unpack_ascii, unpack_data
get_filter, load_filter, set_filter
calc_stat_info, get_stat_info
get_default_id, list_data_ids, list_response_ids, list_stats
get_draws, get_iter_method_name, get_iter_method_opt, get_method, get_method_name, get_method_opt
clean, get_model, 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_response, get_source, get_source_component_image, get_source_component_plot, get_source_contour, get_source_image, get_source_plot, image_source
get_split_plot, plot_data, set_xlinear, set_xlog, set_ylinear, set_ylog
get_psf, get_psf_contour, get_psf_image, get_psf_plot
save_error, save_filter, save_grouping, save_quality, save_staterror, save_syserror
get_chisqr_plot, get_delchi_plot, get_prior, get_sampler, get_stat, get_stat_name
calc_data_sum, calc_data_sum2d, calc_ftest, calc_kcorr, calc_mlr, calc_model_sum2d, calc_source_sum2d, get_analysis, get_rate
contour, contour_data, contour_ratio, histogram1d, histogram2d, image_data, image_getregion, rebin