get_grouping¶
-
sherpa.astro.ui.
get_grouping
(id=None, bkg_id=None)¶ Return the grouping array for a PHA data set.
The function returns the grouping value for each channel in the PHA data set.
- 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.
bkg_id (int or str, optional) – Set if the grouping flags should be taken from a background associated with the data set.
- Returns
grouping – A value of
1
indicates the start of a new group, and-1
indicates that the bin is part of the group. This array is not filtered - that is, there is one element for each channel in the PHA data set. Changes to the elements of this array will change the values in the dataset (it is a reference to the values used to define the quality, not a copy).- Return type
ndarray or
None
- Raises
sherpa.utils.err.ArgumentErr – If the data set does not contain a PHA data set.
See also
fit
Fit one or more data sets.
get_quality
Return the quality array for a PHA data set.
ignore_bad
Exclude channels marked as bad in a PHA data set.
load_grouping
Load the grouping scheme from a file and add to a PHA data set.
set_grouping
Apply a set of grouping flags to a PHA data set.
Notes
The meaning of the grouping column is taken from 1, which says that +1 indicates the start of a bin, -1 if the channel is part of group, and 0 if the data grouping is undefined for all channels.
References
- 1
“The OGIP Spectral File Format”, https://heasarc.gsfc.nasa.gov/docs/heasarc/ofwg/docs/spectra/ogip_92_007/ogip_92_007.html
Examples
Copy the grouping array from the default data set to data set 2:
>>> grp1 = get_grouping() >>> set_grouping(2, grp1)
Return the grouping array of the background component labelled 2 for the ‘histate’ data set:
>>> grp = get_grouping('histate', bkg_id=2)