SpectrumDatasetOnOff

class gammapy.spectrum.SpectrumDatasetOnOff(model=None, counts=None, counts_off=None, livetime=None, mask_fit=None, aeff=None, edisp=None, mask_safe=None)

Bases: gammapy.utils.fitting.Dataset

Compute spectral model fit statistic on a ON OFF Spectrum.

Parameters:

model : SpectralModel

Fit model

counts : PHACountsSpectrum

ON Counts spectrum

counts_off : PHACountsSpectrum

OFF Counts spectrum

livetime : Quantity

Livetime

mask_fit : array

Mask to apply to the likelihood for fitting.

aeff : EffectiveAreaTable

Effective area

edisp : EnergyDispersion

Energy dispersion

mask_safe : array

Mask defining the safe data range.

Attributes Summary

alpha	Exposure ratio between signal and background regions
data_shape	Shape of the counts data
energy_range	Energy range defined by the safe mask.
hi_threshold	High energy threshold
livetime
lo_threshold	Low energy threshold
mask	Combined fit and safe mask
mask_safe	The mask defined by the counts PHACountsSpectrum
model
obs_id	The observation ID of the dataset
parameters
total_stats	Return total SpectrumStats
total_stats_safe_range	Return total SpectrumStats within the tresholds

Methods Summary

copy(self)	A deep copy.
excess(self)	Excess (counts - alpha * counts_off)
from_ogip_files(filename)	Read SpectrumDatasetOnOff from OGIP files.
likelihood(self)	Total likelihood given the current model parameters.
likelihood_per_bin(self)	Likelihood per bin given the current model parameters
npred(self)	Predicted counts vector.
peek(self[, figsize])	Quick-look summary plots.
plot_counts(self[, ax])	Plot predicted and detected counts.
plot_fit(self)	Plot counts and residuals in two panels.
plot_residuals(self[, ax])	Plot residuals.
read(filename)	Read from file
reset_thresholds(self)	Reset energy thresholds (i.e.
residuals(self)	Residuals (npred - excess).
set_fit_energy_range(self[, emin, emax])	Set the energy range for the fit.
stats_in_range(self, bin_min, bin_max)	Compute stats for a range of energy bins.
to_ogip_files(self[, outdir, use_sherpa, …])	Write OGIP files.

Attributes Documentation

alpha

Exposure ratio between signal and background regions

data_shape

Shape of the counts data

energy_range

Energy range defined by the safe mask.

hi_threshold

High energy threshold

livetime

lo_threshold

Low energy threshold

mask

Combined fit and safe mask

mask_safe

The mask defined by the counts PHACountsSpectrum

model

obs_id

The observation ID of the dataset

parameters

total_stats

Return total SpectrumStats

total_stats_safe_range

Return total SpectrumStats within the tresholds

Methods Documentation

copy(self)

A deep copy.

excess(self)

Excess (counts - alpha * counts_off)

classmethod from_ogip_files(filename)

Read SpectrumDatasetOnOff from OGIP files.

BKG file, ARF, and RMF must be set in the PHA header and be present in the same folder.

Parameters:

filename : str

OGIP PHA file to read

likelihood(self)

Total likelihood given the current model parameters.

likelihood_per_bin(self)

Likelihood per bin given the current model parameters

npred(self)

Predicted counts vector.

peek(self, figsize=(10, 10))

Quick-look summary plots.

plot_counts(self, ax=None)

Plot predicted and detected counts.

Parameters:

ax : Axes

Axes object.

Returns:

ax : Axes

Axes object.

plot_fit(self)

Plot counts and residuals in two panels.

Calls plot_counts and plot_residuals.

plot_residuals(self, ax=None)

Plot residuals.

Parameters:

ax : Axes

Axes object.

Returns:

ax : Axes

Axes object.

classmethod read(filename)

Read from file

For now, filename is assumed to the name of a PHA file where BKG file, ARF, and RMF names must be set in the PHA header and be present in the same folder

Parameters:

filename : str

OGIP PHA file to read

reset_thresholds(self)

Reset energy thresholds (i.e. declare all energy bins valid)

residuals(self)

Residuals (npred - excess).

set_fit_energy_range(self, emin=None, emax=None)

Set the energy range for the fit.

Parameters:

emin : Quantity

Minimum energy, default is None (i.e. set to minimal energy)

emax : Quantity

Maximum energy, default is None (i.e. set to maximal energy)

stats_in_range(self, bin_min, bin_max)

Compute stats for a range of energy bins.

Parameters:

bin_min, bin_max: int

Bins to include

Returns:

stats : SpectrumStats

Stacked stats

to_ogip_files(self, outdir=None, use_sherpa=False, overwrite=False)

Write OGIP files.

If you want to use the written files with Sherpa you have to set the use_sherpa flag. Then all files will be written in units ‘keV’ and ‘cm2’.

Parameters:

outdir : pathlib.Path

output directory, default: pwd

use_sherpa : bool, optional

Write Sherpa compliant files, default: False

overwrite : bool

Overwrite existing files?