sine_gaussian_example.py

#!/usr/bin/env python
"""
Tutorial to demonstrate running parameter estimation on a sine gaussian injected signal.

"""
from __future__ import division, print_function
import bilby
import numpy as np

# Set the duration and sampling frequency of the data segment that we're going to inject the signal into
duration = 4.
sampling_frequency = 2048.

# Specify the output directory and the name of the simulation.
outdir = 'outdir'
label = 'sine_gaussian'
bilby.core.utils.setup_logger(outdir=outdir, label=label)

# Set up a random seed for result reproducibility.  This is optional!
np.random.seed(170801)

# We are going to inject a sine gaussian waveform.  We first establish a dictionary of parameters that
# includes all of the different waveform parameters
injection_parameters = dict(hrss = 1e-22, Q = 5.0, frequency = 200.0, ra = 1.375, dec = -1.2108, 
                             geocent_time = 1126259642.413, psi= 2.659)

# Create the waveform_generator using a sine Gaussian source function
waveform_generator = bilby.gw.waveform_generator.WaveformGenerator(duration=duration,
                                                                   sampling_frequency=sampling_frequency,
                                                                   frequency_domain_source_model=bilby.gw.source.sinegaussian,
                                                                   parameters=injection_parameters)

# Set up interferometers.  In this case we'll use three interferometers (LIGO-Hanford (H1), LIGO-Livingston (L1),
# and Virgo (V1)).  These default to their design sensitivity
ifos = bilby.gw.detector.InterferometerList(['H1', 'L1', 'V1'])
ifos.set_strain_data_from_power_spectral_densities(
    sampling_frequency=sampling_frequency, duration=duration,
    start_time=injection_parameters['geocent_time']-3)
ifos.inject_signal(waveform_generator=waveform_generator,
                   parameters=injection_parameters)

# Set up prior, which is a dictionary
priors = dict()
# By default we will sample all terms in the signal models.  However, this will take a long time for the calculation,
# so for this example we will set almost all of the priors to be equall to their injected values.  This implies the
# prior is a delta function at the true, injected value.  In reality, the sampler implementation is smart enough to
# not sample any parameter that has a delta-function prior.
for key in ['psi', 'ra', 'dec', 'geocent_time']:
    priors[key] = injection_parameters[key]

# The above list does *not* include frequency and Q, which means those are the parameters
# that will be included in the sampler.  If we do nothing, then the default priors get used.
#priors['Q'] = bilby.prior.create_default_prior(name='Q')
#priors['frequency'] = bilby.prior.create_default_prior(name='frequency')
priors['Q'] = bilby.core.prior.Uniform(2, 50, 'Q')
priors['frequency'] = bilby.core.prior.Uniform(30, 1000, 'frequency', unit='Hz')
priors['hrss'] = bilby.core.prior.Uniform(1e-23, 1e-21, 'hrss')

# Initialise the likelihood by passing in the interferometer data (IFOs) and the waveoform generator
likelihood = bilby.gw.likelihood.GravitationalWaveTransient(interferometers=ifos, waveform_generator=waveform_generator)

# Run sampler.  In this case we're going to use the `dynesty` sampler
result = bilby.core.sampler.run_sampler(likelihood=likelihood, priors=priors, sampler='dynesty', npoints=1000,
                                        injection_parameters=injection_parameters, outdir=outdir, label=label)

# make some plots of the outputs
result.plot_corner()