SpectrumDatasetOnOff¶
-
class
gammapy.datasets.
SpectrumDatasetOnOff
(models=None, counts=None, counts_off=None, livetime=None, aeff=None, edisp=None, mask_safe=None, mask_fit=None, acceptance=None, acceptance_off=None, name=None, gti=None)[source]¶ Bases:
gammapy.datasets.SpectrumDataset
Spectrum dataset for on-off likelihood fitting.
The on-off spectrum dataset bundles reduced counts data, off counts data, with a spectral model, relative background efficiency and instrument response functions to compute the fit-statistic given the current model and data.
- Parameters
- models
Models
Fit model
- counts
RegionNDMap
ON Counts spectrum
- counts_off
RegionNDMap
OFF Counts spectrum
- livetime
Quantity
Livetime
- aeff
EffectiveAreaTable
Effective area
- edisp
EDispKernel
Energy dispersion
- mask_safe
RegionNDMap
Mask defining the safe data range.
- mask_fit
RegionNDMap
Mask to apply to the likelihood for fitting.
- acceptance
RegionNDMap
or float Relative background efficiency in the on region.
- acceptance_off
RegionNDMap
or float Relative background efficiency in the off region.
- namestr
Name of the dataset.
- gti
GTI
GTI of the observation or union of GTI if it is a stacked observation
- models
See also
Attributes Summary
Exposure ratio between signal and background regions
Shape of the counts data
Energy range defined by the safe mask
Model evaluators
Excess (counts - alpha * counts_off)
Excess (aeff * livetime)
Combined fit and safe mask
Models (
gammapy.modeling.models.Models
).Methods Summary
copy
(self[, name])A deep copy.
create
(e_reco[, e_true, region, …])Create empty SpectrumDatasetOnOff.
fake
(self, background_model[, random_state])Simulate fake counts for the current model and reduced irfs.
from_dict
(data, models)Create flux point dataset from dict.
from_ogip_files
(filename)Read
SpectrumDatasetOnOff
from OGIP files.from_spectrum_dataset
(dataset, acceptance, …)Create spectrum dataseton off from another dataset.
info_dict
(self[, in_safe_energy_range])Info dict with summary statistics, summed over energy
npred
(self)Return npred map (model + background)
npred_sig
(self)Predicted counts from source model (
RegionNDMap
).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[, method, ax])Plot residuals.
read
(filename)Read from file
residuals
(self[, method])Compute the spectral residuals.
stack
(self, other)Stack this dataset with another one.
stat_array
(self)Likelihood per bin given the current model parameters
stat_sum
(self)Total statistic given the current model parameters.
to_dict
(self, filename, \*args, \*\*kwargs)Convert to dict for YAML serialization.
to_ogip_files
(self[, outdir, use_sherpa, …])Write OGIP files.
write
(self, filename, overwrite)Write spectrum dataset on off to file.
Attributes Documentation
-
alpha
¶ Exposure ratio between signal and background regions
-
background
¶
-
data_shape
¶ Shape of the counts data
-
energy_range
¶ Energy range defined by the safe mask
-
evaluators
¶ Model evaluators
-
excess
¶ Excess (counts - alpha * counts_off)
-
exposure
¶ Excess (aeff * livetime)
-
mask
¶ Combined fit and safe mask
-
mask_safe
¶
-
models
¶ Models (
gammapy.modeling.models.Models
).
-
name
¶
-
stat_type
= 'wstat'¶
-
tag
= 'SpectrumDatasetOnOff'¶
Methods Documentation
-
copy
(self, name=None)¶ A deep copy.
-
classmethod
create
(e_reco, e_true=None, region=None, reference_time='2000-01-01', name=None)[source]¶ Create empty SpectrumDatasetOnOff.
Empty containers are created with the correct geometry. counts, counts_off and aeff are zero and edisp is diagonal.
The safe_mask is set to False in every bin.
-
fake
(self, background_model, random_state='random-seed')[source]¶ Simulate fake counts for the current model and reduced irfs.
This method overwrites the counts and off counts defined on the dataset object.
- Parameters
- background_model
RegionNDMap
Background model.
- random_state{int, ‘random-seed’, ‘global-rng’,
RandomState
} Defines random number generator initialisation. Passed to
get_random_state
.
- background_model
-
classmethod
from_dict
(data, models)[source]¶ Create flux point dataset from dict.
- Parameters
- datadict
Dict containing data to create dataset from.
- modelslist of
SkyModel
List of model components.
- Returns
- dataset
SpectrumDatasetOnOff
Spectrum dataset on off.
- dataset
-
classmethod
from_ogip_files
(filename)[source]¶ Read
SpectrumDatasetOnOff
from OGIP files.BKG file, ARF, and RMF must be set in the PHA header and be present in the same folder.
The naming scheme is fixed to the following scheme:
PHA file is named
pha_obs{name}.fits
BKG file is named
bkg_obs{name}.fits
ARF file is named
arf_obs{name}.fits
RMF file is named
rmf_obs{name}.fits
with{name}
the dataset name.
- Parameters
- filenamestr
OGIP PHA file to read
-
classmethod
from_spectrum_dataset
(dataset, acceptance, acceptance_off, counts_off=None)[source]¶ Create spectrum dataseton off from another dataset.
- Parameters
- dataset
SpectrumDataset
Spectrum dataset defining counts, edisp, aeff, livetime etc.
- acceptance
array
or float Relative background efficiency in the on region.
- acceptance_off
array
or float Relative background efficiency in the off region.
- counts_off
RegionNDMap
Off counts spectrum . If the dataset provides a background model, and no off counts are defined. The off counts are deferred from counts_off / alpha.
- dataset
- Returns
- dataset
SpectrumDatasetOnOff
Spectrum dataset on off.
- dataset
-
info_dict
(self, in_safe_energy_range=True)[source]¶ Info dict with summary statistics, summed over energy
- Parameters
- in_safe_energy_rangebool
Whether to sum only in the safe energy range
- Returns
- info_dictdict
Dictionary with summary info.
-
npred
(self)¶ Return npred map (model + background)
-
npred_sig
(self)¶ Predicted counts from source model (
RegionNDMap
).
-
peek
(self, figsize=(16, 4))¶ Quick-look summary plots.
-
plot_counts
(self, ax=None)¶ Plot predicted and detected counts.
- Parameters
- ax
Axes
Axes object.
- ax
- Returns
- ax
Axes
Axes object.
- ax
-
plot_fit
(self)¶ Plot counts and residuals in two panels.
Calls
plot_counts
andplot_residuals
.
-
plot_residuals
(self, method='diff', ax=None, **kwargs)¶ Plot residuals.
- Parameters
- ax
Axes
Axes object.
- method{“diff”, “diff/model”, “diff/sqrt(model)”}
Normalization used to compute the residuals, see
SpectrumDataset.residuals()
- **kwargsdict
Keywords passed to
RegionNDMap.plot()
- ax
- Returns
- ax
Axes
Axes object.
- ax
-
classmethod
read
(filename)[source]¶ 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
- filenamestr
OGIP PHA file to read
-
residuals
(self, method='diff')¶ Compute the spectral residuals.
- Parameters
- method{“diff”, “diff/model”, “diff/sqrt(model)”}
- Method used to compute the residuals. Available options are:
diff
(default): data - modeldiff/model
: (data - model) / modeldiff/sqrt(model)
: (data - model) / sqrt(model)
- Returns
- residuals
RegionNDMap
Residual spectrum
- residuals
-
stack
(self, other)[source]¶ Stack this dataset with another one.
Safe mask is applied to compute the stacked counts vector. Counts outside each dataset safe mask are lost.
Stacking is performed in-place.
The stacking of 2 datasets is implemented as follows. Here, \(k\) denotes a bin in reconstructed energy and \(j = {1,2}\) is the dataset number
The
mask_safe
of each dataset is defined as:\[\begin{split}\epsilon_{jk} =\left\{\begin{array}{cl} 1, & \mbox{if k is inside the energy thresholds}\\ 0, & \mbox{otherwise} \end{array}\right.\end{split}\]Then the total
counts
andcounts_off
are computed according to:\[ \begin{align}\begin{aligned}\overline{\mathrm{n_{on}}}_k = \mathrm{n_{on}}_{1k} \cdot \epsilon_{1k} + \mathrm{n_{on}}_{2k} \cdot \epsilon_{2k}\\\overline{\mathrm{n_{off}}}_k = \mathrm{n_{off}}_{1k} \cdot \epsilon_{1k} + \mathrm{n_{off}}_{2k} \cdot \epsilon_{2k}\end{aligned}\end{align} \]The stacked
safe_mask
is then:\[\overline{\epsilon_k} = \epsilon_{1k} OR \epsilon_{2k}\]In each energy bin \(k\), the count excess is computed taking into account the ON
acceptance
, \(a_{on}_k\) and the OFF one:acceptance_off
, \(a_{off}_k\). They define the \(\alpha_k=a_{on}_k/a_{off}_k\) factors such that \(n_{ex}_k = n_{on}_k - \alpha_k n_{off}_k\). We define the stacked value of \(\overline{{a}_{on}}_k = 1\) so that:\[\overline{{a}_{off}}_k = \frac{\overline{\mathrm {n_{off}}}}{\alpha_{1k} \cdot \mathrm{n_{off}}_{1k} \cdot \epsilon_{1k} + \alpha_{2k} \cdot \mathrm{n_{off}}_{2k} \cdot \epsilon_{2k}}\]Please refer to the
IRFStacker
for the description of how the IRFs are stacked.- Parameters
- other
SpectrumDatasetOnOff
the dataset to stack to the current one
- other
Examples
>>> from gammapy.datasets import SpectrumDatasetOnOff >>> obs_ids = [23523, 23526, 23559, 23592] >>> datasets = [] >>> for obs in obs_ids: >>> filename = "$GAMMAPY_DATA/joint-crab/spectra/hess/pha_obs{}.fits" >>> ds = SpectrumDatasetOnOff.from_ogip_files(filename.format(obs)) >>> datasets.append(ds) >>> stacked = datasets[0] >>> for ds in datasets[1:]: >>> stacked.stack(ds) >>> print(stacked.livetime) 6313.8116406202325 s
-
stat_sum
(self)¶ Total statistic given the current model parameters.
-
to_ogip_files
(self, outdir=None, use_sherpa=False, overwrite=False)[source]¶ 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’.The naming scheme is fixed, with {name} the dataset name:
PHA file is named pha_obs{name}.fits
BKG file is named bkg_obs{name}.fits
ARF file is named arf_obs{name}.fits
RMF file is named rmf_obs{name}.fits
- Parameters
- outdir
pathlib.Path
output directory, default: pwd
- use_sherpabool, optional
Write Sherpa compliant files, default: False
- overwritebool
Overwrite existing files?
- outdir