# save_delchi¶

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

Save the ratio of residuals (data-model) to error to a file.

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 residuals 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). sherpa.utils.err.IdentifierErr – If no model has been set for this data set. sherpa.utils.err.IOErr – If filename already exists and clobber is False.

save_data()
Save the data to a file.
save_resid()
Save the residuals (data-model) 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 DELCHI. The residuals array respects any filter or (for PHA files), grouping settings.

Examples

Write the residuals to the file “delchi.dat”:

>>> save_delchi('delchi.dat')


Write the residuals from the data set ‘jet’ to the FITS file “delchi.fits”:

>>> save_delchi('jet', "delchi.fits", ascii=False)