load_staterror

sherpa.astro.ui.load_staterror(id, filename=None, bkg_id=None, *args, **kwargs)

Load the statistical errors from a file.

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.

Parameters:
  • 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 or str, 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 '#'.

See also

get_staterror()
Return the statistical error on the dependent axis of a data set.
load_syserror()
Load the systematic errors from a file.
set_staterror()
Set the statistical errors on the dependent axis of a data set.
set_stat()
Set the statistical method.

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.

Examples

Read in the first column from ‘tbl.dat’:

>>> load_staterror('tbl.dat')

Use the column labelled ‘col3’

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

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]')

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

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

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')