Last modified: December 2023

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AHELP for CIAO 4.16 Sherpa


Context: data


Load the statistical errors from a file.


load_staterror(id, filename=None, bkg_id=None, *args, **kwargs)

id - int or str, optional
filename - str
bkg_id - int or str, optional
colkeys - array of str, optional
sep - str, optional
comment - str, optional


Read in a column or image from a file and use the values as the statistical errors for a data set. This over rides the errors calculated by any statistic, such as chi2gehrels or chi2datavar .


Example 1

Read in the first column from 'tbl.dat':

>>> load_staterror('tbl.dat')

Example 2

Use the column labelled 'col3'

>>> load_staterror('tbl.dat', colkeys=['col3'])

Example 3

When using the Crates I/O library, the file name can include CIAO Data Model syntax, such as column selection:

>>> load_staterror('tbl.dat[cols col3]')

Example 4

Read in the first column from the file 'errors.fits' as the statistical errors for the 'core' data set:

>>> load_staterror('core', 'errors.fits')

Example 5

The data set labelled 'img' is loaded from the file 'image.fits' and the statistical errors from 'err.fits'. The dimensions of the two images must be the same.

>>> load_image('img', 'image.fits')
>>> load_staterror('img', 'err.fits')


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` .
filename The name of the file to read in. Supported formats depends on the I/O library in use (Crates or AstroPy) and the type of data set (e.g. 1D or 2D).
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.
colkeys An array of the column name to read in. The default is none .
sep The separator character. The default is ' ' .
comment The comment character. The default is '#' .


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 `filename` parameter. If given two un-named arguments, then they are interpreted as the `id` and `filename` parameters, respectively. The remaining parameters are expected to be given as named arguments.


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

See Also

dataspace1d, dataspace2d, datastack, fake, load_arf, load_arrays, load_ascii, load_bkg, load_bkg_arf, load_bkg_rmf, load_data, load_grouping, load_image, load_multi_arfs, load_multi_rmfs, load_pha, load_quality, load_rmf, load_syserror, load_table, pack_image, pack_pha, pack_table, set_staterror, unpack_arf, unpack_arrays, unpack_ascii, unpack_bkg, unpack_data, unpack_image, unpack_pha, unpack_rmf, unpack_table
get_default_id, list_bkg_ids, list_data_ids
add_model, add_user_pars, load_table_model, load_template_interpolator, load_template_model, load_user_model, save_model, save_source
save_arrays, save_data, save_delchi, save_error, save_filter, save_grouping, save_image, save_pha, save_quality, save_resid, save_staterror, save_syserror, save_table