calc_source_sum¶

sherpa.astro.ui.calc_source_sum(lo=None, hi=None, id=None, bkg_id=None)¶

Sum up the source model over a pass band.

Sum up S(E) over a pass band, where S(E) is the spectral model evaluated for each bin (that is, the model without any instrumental responses applied to it).

Parameters:	lo (number, optional) – The minimum limit of the band. Use `None`, the default, to use the low value of the data set. hi (number, optional) – The maximum limit of the band, which must be larger than `lo`. Use `None`, the default, to use the upper value of the data set. id (int or str, optional) – Use the source expression associated with this data set. If not given then the default identifier is used, as returned by get_default_id. bkg_id (int or str, optional) – If set, use the model associated with the given background component rather than the source model.
Returns:	signal – The source model summed up over the given band. This does not include the bin width when using histogram-style (‘integrated’ data spaces), such as used with X-Spec emission - also known as additive - models.
Return type:	number

See also

calc_data_sum(): Sum up the observed counts over a pass band.
calc_model_sum(): Sum up the fitted model over a pass band.
calc_energy_flux(): Integrate the source model over a pass band.
calc_photon_flux(): Integrate the source model over a pass band.
set_model(): Set the source model expression for a data set.

Notes

The units of lo and hi are determined by the analysis setting for the data set (e.g. get_analysis).

Any existing filter on the data set - e.g. as created by ignore or notice - is ignored by this function.

The units of the answer depend on the model components used in the source expression and the axis or axes of the data set. It is unlikely to give sensible results for 2D data sets.

Examples

Sum up the model over the data range 0.5 to 2 for the default data set:

>>> calc_source_sum(0.5, 2)
139.12819041922018

Compare the output of the calc_source_sum and calc_photon_flux routines. A 1099-bin data space is created, with a model which has a value of 1 for each bin. As the bin width is constant, at 0.01, the integrated value, calculated by calc_photon_flux, is one hundredth the value from calc_data_sum:

>>> dataspace1d(0.01, 11, 0.01, id="test")
>>> set_source("test", const1d.bflat)
>>> bflat.c0 = 1
>>> calc_source_sum(id="test")
1099.0
>>> calc_photon_flux(id="test")
10.99