Last modified: December 2020

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

set_staterror

Context: data

Synopsis

Set the statistical errors on the dependent axis of a data set.

Syntax

set_staterror(id, val=None, fractional=False, bkg_id=None)

id - int or str, optional
val - array or scalar
fractional - bool, optional
bkg_id - int or str, optional

Description

These values over-ride the errors calculated by any statistic, such as chi2gehrels or chi2datavar .


Examples

Example 1

Set the statistical error for the default data set to the value in dys (a scalar or an array):

>>> set_staterror(dys)

Example 2

Set the statistical error on the 'core' data set to be 5% of the data values:

>>> set_staterror('core', 0.05, fractional=True)

PARAMETERS

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` .
val The systematic error.
fractional If False (the default value), then the `val` parameter is the absolute value, otherwise the `val` parameter represents the fractional error, so the absolute value is calculated as get_dep() * val (and `val` must be a scalar).
bkg_id Set to identify which background component to set. The default value ( none ) means that this is for the source component of the data set.

Notes

The function does not follow the normal Python standards for parameter use, since it is designed for easy interactive use. When called with a single un-named argument, it is taken to be the `val` parameter. If given two un-named arguments, then they are interpreted as the `id` and `val` parameters, respectively.


Bugs

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

See Also

confidence
set_conf_opt, set_covar_opt, set_proj_opt
data
load_staterror, set_areascal, set_arf, set_backscal, set_bkg, set_coord, set_counts, set_data, set_dep, set_exposure, set_grouping, set_quality, set_rmf, set_syserror
filtering
set_filter
methods
set_iter_method, set_iter_method_opt, set_method, set_method_opt
modeling
get_par, get_xsabund, get_xscosmo, get_xsxsect, get_xsxset, set_bkg_model, set_bkg_source, set_full_model, set_model, set_par, set_pileup_model, set_source, set_xsabund, set_xscosmo, set_xsxsect, set_xsxset
statistics
set_prior, set_sampler, set_sampler_opt, set_stat
utilities
set_analysis, set_default_id
visualization
image_setregion