Last modified: December 2020

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

get_covar_results

Context: confidence

Synopsis

Return the results of the last covar run.

Syntax

get_covar_results()

Alias: get_covariance_results

Examples

Example 1

>>> res = get_covar_results()
>>> print(res)
datasets    = (1,)
methodname  = covariance
iterfitname = none
fitname     = levmar
statname    = chi2gehrels
sigma       = 1
percent     = 68.2689492137
parnames    = ('bgnd.c0',)
parvals     = (10.228675427602724,)
parmins     = (-2.4896739438296795,)
parmaxes    = (2.4896739438296795,)
nfits       = 0

Example 2

In this case, of a single parameter, the covariance matrix is just the variance of the parameter:

>>> res.extra_output
array([[ 6.19847635]])

Notes

The fields of the object include:

Item Definition
datasets A tuple of the data sets used in the analysis.
methodname This will be 'covariance'.
iterfitname The name of the iterated-fit method used, if any.
fitname The name of the optimization method used.
statname The name of the fit statistic used.
sigma The sigma value used to calculate the confidence intervals.
percent The percentage of the signal contained within the confidence intervals (calculated from the sigma value assuming a normal distribution).
parnames A tuple of the parameter names included in the analysis.
parvals A tuple of the best-fit parameter values, in the same order as parnames .
parmins A tuple of the lower error bounds, in the same order as parnames .
parmaxes A tuple of the upper error bounds, in the same order as parnames .
nfits The number of model evaluations.

There is also an extra_output field which is used to return the covariance matrix.


Bugs

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

See Also

confidence
conf, confidence, covar, covariance, get_conf, get_conf_results, get_covar, get_covar_opt, 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, int_proj, int_unc, proj, projection, reg_proj, reg_unc, set_conf_opt, set_covar_opt, set_proj_opt
contrib
get_chart_spectrum, get_marx_spectrum
data
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_staterror, get_syserror
filtering
get_filter
fitting
calc_stat_info, get_stat_info
info
get_default_id, list_stats
methods
get_draws, get_iter_method_name, get_iter_method_opt, get_method, get_method_name, get_method_opt
modeling
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
plotting
get_split_plot
psfs
get_psf, get_psf_contour, get_psf_image, get_psf_plot
statistics
get_chisqr_plot, get_delchi_plot, get_prior, get_sampler, get_stat, get_stat_name
utilities
get_analysis, get_rate
visualization
image_getregion