save_error

sherpa.astro.ui.save_error(id, filename=None, bkg_id=None, ascii=True, clobber=False)

Save the errors to a file.

The total errors for a data set are the quadrature combination of the statistical and systematic errors. The systematic errors can be 0. If the statistical errors have not been set explicitly, then the values calculated by the statistic - such as chi2gehrels or chi2datavar - will be used.

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 write the array to. The format is determined by the ascii argument.
  • bkg_id (int or str, optional) – Set if the background should be written out rather than the source.
  • ascii (bool, optional) – If False then the data is written as a FITS format binary table. The default is True. The exact format of the output file depends on the I/O library in use (Crates or AstroPy).
  • clobber (bool, optional) – If outfile is not None, then this flag controls whether an existing file can be overwritten (True) or if it raises an exception (False, the default setting).
Raises:

sherpa.utils.err.IOErr – If filename already exists and clobber is False.

See also

get_error()
Return the errors on the dependent axis of a data set.
load_staterror()
Load the statistical errors from a file.
load_syserror()
Load the systematic errors from a file.
save_data()
Save the data to a file.
save_staterror()
Save the statistical errors to a file.
save_syserror()
Save the systematic errors to a file.

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.

The output file contains the columns X and ERR.

Examples

Write out the errors from the default data set to the file ‘errs.dat’.

>>> save_error('errs.dat')

Over-write the file it it already exists, and take the data from the data set “jet”:

>>> save_error('jet', 'err.out', clobber=True)

Write the data out in FITS format:

>>> save_error('err.fits', ascii=False)