load_staterror

Context: data

Synopsis

Load the statistical errors from a file.

Syntax

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

Description

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 .

Examples

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')

PARAMETERS

The parameters for this function are:

Parameter	Type information	Definition
id	int or str, optional	The identifier for the data set to use. If not given then the default identifier is used, as returned by `get_default_id` .
filename	str	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	int, str, or None, optional	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	array of str, optional	An array of the column name to read in. The default is none .
sep	str, optional	The separator character. The default is ' ' .
comment	str, optional	The comment character. The default is '#' .

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 `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.

Bugs

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