# Licensed under a 3-clause BSD style license - see LICENSE.rst
import copy
import logging
import numpy as np
import astropy.units as u
from astropy.convolution import Tophat2DKernel
from astropy.coordinates import Angle
from gammapy.datasets import MapDataset, MapDatasetOnOff
from gammapy.maps import Map, MapAxis
from gammapy.stats import CashCountsStatistic, WStatCountsStatistic
from .core import Estimator
from .utils import estimate_exposure_reco_energy
__all__ = [
"ExcessMapEstimator",
]
log = logging.getLogger(__name__)
def convolved_map_dataset_counts_statistics(dataset, kernel, mask):
"""Return CountsDataset objects containing smoothed maps from the MapDataset"""
# Kernel is modified later make a copy here
kernel = copy.deepcopy(kernel)
kernel.normalize("peak")
# fft convolution adds numerical noise, to ensure integer results we call
# np.rint
n_on = dataset.counts * mask
n_on_conv = np.rint(n_on.convolve(kernel.array).data)
if isinstance(dataset, MapDatasetOnOff):
background = dataset.background * mask
background.data[dataset.acceptance_off.data == 0] = 0.0
n_off = dataset.counts_off * mask
background_conv = background.convolve(kernel.array)
n_off_conv = n_off.convolve(kernel.array)
npred_sig = dataset.npred_signal() * mask
mu_sig = npred_sig.convolve(kernel.array)
with np.errstate(invalid="ignore", divide="ignore"):
alpha_conv = background_conv / n_off_conv
return WStatCountsStatistic(
n_on_conv.data, n_off_conv.data, alpha_conv.data, mu_sig.data
)
else:
npred = dataset.npred() * mask
background_conv = npred.convolve(kernel.array)
return CashCountsStatistic(n_on_conv.data, background_conv.data)
[docs]class ExcessMapEstimator(Estimator):
"""Computes correlated excess, sqrt TS (i.e. Li-Ma significance) and errors for MapDatasets.
If a model is set on the dataset the excess map estimator will compute the excess taking into account
the predicted counts of the model.
Parameters
----------
correlation_radius : ~astropy.coordinate.Angle
correlation radius to use
n_sigma : float
Confidence level for the asymmetric errors expressed in number of sigma.
Default is 1.
n_sigma_ul : float
Confidence level for the upper limits expressed in number of sigma.
Default is 3.
selection_optional : list of str
Which additional maps to estimate besides delta TS, significance and symmetric error.
Available options are:
* "errn-errp": estimate asymmetric errors.
* "ul": estimate upper limits.
By default all additional quantities are estimated.
energy_edges : `~astropy.units.Quantity`
Energy edges of the target excess maps bins.
apply_mask_fit : Bool
Apply a mask for the computation.
A `~gammapy.datasets.MapDataset.mask_fit` must be present on the input dataset
"""
tag = "ExcessMapEstimator"
_available_selection_optional = ["errn-errp", "ul"]
def __init__(
self,
correlation_radius="0.1 deg",
n_sigma=1,
n_sigma_ul=3,
selection_optional="all",
energy_edges=None,
apply_mask_fit=False,
):
self.correlation_radius = correlation_radius
self.n_sigma = n_sigma
self.n_sigma_ul = n_sigma_ul
self.apply_mask_fit = apply_mask_fit
self.selection_optional = selection_optional
self.energy_edges = energy_edges
@property
def correlation_radius(self):
return self._correlation_radius
@correlation_radius.setter
def correlation_radius(self, correlation_radius):
"""Sets radius"""
self._correlation_radius = Angle(correlation_radius)
[docs] def run(self, dataset):
"""Compute correlated excess, Li & Ma significance and flux maps
If a model is set on the dataset the excess map estimator will compute the excess taking into account
the predicted counts of the model.
Parameters
----------
dataset : `~gammapy.datasets.MapDataset` or `~gammapy.datasets.MapDatasetOnOff`
input dataset
Returns
-------
images : dict
Dictionary containing result correlated maps. Keys are:
* counts : correlated counts map
* background : correlated background map
* excess : correlated excess map
* ts : TS map
* sqrt_ts : sqrt(delta TS), or Li-Ma significance map
* err : symmetric error map (from covariance)
* flux : flux map. An exposure map must be present in the dataset to compute flux map
* errn : negative error map
* errp : positive error map
* ul : upper limit map
"""
if not isinstance(dataset, MapDataset):
raise ValueError("Unsupported dataset type")
if self.energy_edges is None:
energy_axis = dataset.counts.geom.axes["energy"]
energy_edges = u.Quantity([energy_axis.edges[0], energy_axis.edges[-1]])
else:
energy_edges = self.energy_edges
axis = MapAxis.from_energy_edges(energy_edges)
resampled_dataset = dataset.resample_energy_axis(energy_axis=axis)
# Beware we rely here on the correct npred background in MapDataset.resample_energy_axis
resampled_dataset.models = dataset.models
result = self.estimate_excess_map(resampled_dataset)
return result
[docs] def estimate_excess_map(self, dataset):
"""Estimate excess and ts maps for single dataset.
If exposure is defined, a flux map is also computed.
Parameters
----------
dataset : `MapDataset`
Map dataset
"""
pixel_size = np.mean(np.abs(dataset.counts.geom.wcs.wcs.cdelt))
size = self.correlation_radius.deg / pixel_size
kernel = Tophat2DKernel(size)
geom = dataset.counts.geom
if self.apply_mask_fit:
mask = dataset.mask
elif dataset.mask_safe:
mask = dataset.mask_safe
else:
mask = np.ones(dataset.data_shape, dtype=bool)
counts_stat = convolved_map_dataset_counts_statistics(dataset, kernel, mask)
n_on = Map.from_geom(geom, data=counts_stat.n_on)
bkg = Map.from_geom(geom, data=counts_stat.n_on - counts_stat.n_sig)
excess = Map.from_geom(geom, data=counts_stat.n_sig)
result = {"counts": n_on, "background": bkg, "excess": excess}
tsmap = Map.from_geom(geom, data=counts_stat.ts)
sqrt_ts = Map.from_geom(geom, data=counts_stat.sqrt_ts)
result.update({"ts": tsmap, "sqrt_ts": sqrt_ts})
err = Map.from_geom(geom, data=counts_stat.error * self.n_sigma)
result.update({"err": err})
if dataset.exposure:
reco_exposure = estimate_exposure_reco_energy(dataset)
flux = excess / reco_exposure
flux.quantity = flux.quantity.to("1 / (cm2 s)")
else:
flux = Map.from_geom(
geom=dataset.counts.geom, data=np.nan * np.ones(dataset.data_shape)
)
result.update({"flux": flux})
if "errn-errp" in self.selection_optional:
errn = Map.from_geom(geom, data=counts_stat.compute_errn(self.n_sigma))
errp = Map.from_geom(geom, data=counts_stat.compute_errp(self.n_sigma))
result.update({"errn": errn, "errp": errp})
if "ul" in self.selection_optional:
ul = Map.from_geom(
geom, data=counts_stat.compute_upper_limit(self.n_sigma_ul)
)
result.update({"ul": ul})
# return nan values outside mask
for key in result:
result[key].data[~mask] = np.nan
return result