calc_source_sum

Synopsis

Sum up the source model over a pass band.

Syntax

calc_source_sum(lo=None, hi=None, id=None, bkg_id=None)

Description

Sum up S(E) over a range of bins, where S(E) is the per-bin model value before it has been convolved with any instrumental response (e.g. RMF and ARF or PSF). This is intended for one-dimensional data sets: use `calc_source_sum2d` for two-dimensional data sets. The `calc_model_sum` function is used to calculate the sum of the model after any instrumental response is applied.

Examples

Example 1

Calculate the model evaluated over the full data set (all points or pixels of the independent axis) for the default data set, and compare it to the sum for th first background component:

>>> tsrc = calc_source_sum()
>>> tbkg = calc_source_sum(bkg_id=1)

Example 2

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

Example 3

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 returned by `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

Example 4

In the following example, a small data set is created, covering the axis range of -5 to 5, and an off-center gaussian model created (centered at 1). The model is evaluated over the full data grid and then a subset of pixels. As the summation is done over those points in the data set that lie within the requested range, the sum for lo=-2 to hi=1 is the same as that for lo=-1.5 to hi=1.5:

>>> load_arrays('test', [-5, -2.5, 0, 2.5, 5], [2, 5, 12, 7, 3])
>>> set_source('test', gauss1d.gmdl)
>>> gmdl.pos = 1
>>> gmdl.fwhm = 2.4
>>> gmdl.ampl = 10
>>> calc_source_sum(id='test')
9.597121089731253
>>> calc_source_sum(-2, 1, id='test')
6.179472329646446
>>> calc_source_sum(-1.5, 1.5, id='test')
6.179472329646446

PARAMETERS

The parameters for this function are:

Parameter	Type information	Definition
lo	number, optional	If both are None or both are set then sum up over the given band. If only one is set then use the model value in the selected bin. The units for `lo` and `hi` are given by the current analysis setting.
hi	number, optional	If both are None or both are set then sum up over the given band. If only one is set then use the model value in the selected bin. The units for `lo` and `hi` are given by the current analysis setting.
id	int, str, or None, 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, str, or None, optional	If set, use the model associated with the given background component rather than the source model.

Return value

The return value from this function is:

signal -- The model value (sum or individual bin).

Notes

The units of lo and hi are determined by the analysis setting for the data set (e.g. `get_analysis` ). The summation occurs over those points in the data set that lie within this range, not the range itself.

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.

Bugs

See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.