Source code for gammapy.data.obs_stats

# Licensed under a 3-clause BSD style license - see LICENSE.rst
import astropy.units as u
from ..stats import Stats, significance_on_off

__all__ = ["ObservationStats"]


[docs]class ObservationStats(Stats): """Observation statistics. Class allowing to summarize observation (`~gammapy.data.DataStoreObservation`) statistics Parameters ---------- n_on : int Number of on events n_off : int Number of off events a_on : float Relative background exposure of the on region a_off : float Relative background exposure of the off region obs_id : int ID of the observation livetime : `~astropy.units.Quantity` Livetime of the observation """ def __init__( self, n_on=None, n_off=None, a_on=None, a_off=None, obs_id=None, livetime=None ): super().__init__(n_on=n_on, n_off=n_off, a_on=a_on, a_off=a_off) self.obs_id = obs_id self.livetime = livetime if a_off > 0: self.alpha_obs = a_on / a_off else: self.alpha_obs = 0 self.gamma_rate = self.excess / livetime self.bg_rate = self.alpha_obs * n_off / livetime
[docs] @classmethod def from_observation(cls, observation, bg_estimate): """Create from `~gammapy.data.DataStoreObservation`. Parameters ---------- observation : `~gammapy.data.DataStoreObservation` IACT data store observation bg_estimate : `~gammapy.background.BackgroundEstimate` Background estimate """ n_on = len(bg_estimate.on_events.table) n_off = len(bg_estimate.off_events.table) a_on = bg_estimate.a_on a_off = bg_estimate.a_off obs_id = observation.obs_id livetime = observation.observation_live_time_duration stats = cls( n_on=n_on, n_off=n_off, a_on=a_on, a_off=a_off, obs_id=obs_id, livetime=livetime, ) return stats
@property def alpha(self): """Alpha (on / off exposure ratio). Override member function from `~gammapy.stats.Stats` to take into account weighted alpha by number of Off events """ return self.alpha_obs @property def sigma(self): """Li-Ma significance for observation statistics (float).""" return significance_on_off(self.n_on, self.n_off, self.alpha, method="lima")
[docs] @classmethod def stack(cls, stats_list): """Stack (concatenate) list of `~gammapy.data.ObservationStats`. Parameters ---------- stats_list : list List of `~gammapy.data.ObservationStats` Returns ------- total_stats : `~gammapy.data.ObservationStats` Statistics for stacked observation """ n_on = 0 n_off = 0 a_on = 0 a_on_backup = 0 a_off = 0 a_off_backup = 0 obs_id = [] livetime = 0 for stats in stats_list: if stats.a_off > 0: livetime += stats.livetime n_on += stats.n_on n_off += stats.n_off a_on += stats.a_on * stats.n_off a_on_backup += stats.a_on * stats.livetime.value a_off += stats.a_off * stats.n_off a_off_backup += stats.a_off * stats.livetime.value obs_id.append(stats.obs_id) # if no off events the weighting of exposure is done # with the livetime if n_off == 0: a_on = a_on_backup / livetime.value a_off = a_off_backup / livetime.value else: a_on /= n_off a_off /= n_off return cls( n_on=n_on, n_off=n_off, a_on=a_on, a_off=a_off, obs_id=obs_id, livetime=livetime, )
[docs] def to_dict(self): """Data as a dict. This is useful for serialization or putting the info in a table. """ return { "obs_id": self.obs_id, "livetime": self.livetime.to("min"), "n_on": self.n_on, "n_off": self.n_off, "a_on": self.a_on, "a_off": self.a_off, "alpha": self.alpha, "background": self.background, "excess": self.excess, "sigma": self.sigma, "gamma_rate": self.gamma_rate.to("1/min"), "bg_rate": self.bg_rate.to("1/min"), }
def __str__(self): ss = "*** Observation summary report ***\n" if type(self.obs_id) is list: obs_str = "[{}-{}]".format(self.obs_id[0], self.obs_id[-1]) else: obs_str = "{}".format(self.obs_id) ss += "Observation Id: {}\n".format(obs_str) ss += "Livetime: {:.3f}\n".format(self.livetime.to(u.h)) ss += "On events: {}\n".format(self.n_on) ss += "Off events: {}\n".format(self.n_off) ss += "Alpha: {:.3f}\n".format(self.alpha) ss += "Bkg events in On region: {:.2f}\n".format(self.background) ss += "Excess: {:.2f}\n".format(self.excess) if self.background > 0: ss += "Excess / Background: {:.2f}\n".format(self.excess / self.background) ss += "Gamma rate: {:.2f}\n".format(self.gamma_rate.to("1/min")) ss += "Bkg rate: {:.2f}\n".format(self.bg_rate.to("1/min")) ss += "Sigma: {:.2f}\n".format(self.sigma) return ss