detailed tutorial for open data

examples/open_data_examples/GW150914_advanced.py

+#!/usr/bin/env python
+"""
+This tutorial includes advanced specifications for analysing known events.
+Here GW150914 is used as an example.
+
+LIST OF AVAILABLE EVENTS: Run -> help(bilby.gw.utils.get_event_time(event))
+"""
+from __future__ import division, print_function
+import bilby
+
+outdir = 'outdir'
+label = 'GW150914'
+time_of_event = bilby.gw.utils.get_event_time(label)
+
+bilby.core.utils.setup_logger(outdir=outdir, label=label)
+
+# GET DATA FROM INTERFEROMETER
+interferometer_names = ['H1', 'L1']  # can also include 'V1'
+duration = 4    # length of data segment containing the signal
+roll_off = 0.2  # smoothness of transition from no signal
+# to max signal in a Tukey Window.
+psd_offset = -1024  # PSD is estimated using data from
+# 'center_time + psd_offset' to 'center_time + psd_offset + psd_duration'
+psd_duration = 100
+filter_freq = None  # low pass filter frequency to cut signal content above
+# Nyquist frequency. The condition is 2 * filter_freq >= sampling_frequency
+
+# Keyword args are passed to 'gwpy.timeseries.TimeSeries.fetch_open_data()'
+# sample_rate: most data are stored by LOSC at 4096 Hz,
+# there may be event-related data releases with a 16384 Hz rate.
+kwargs = {"sample_rate": 4096}
+# For some events a "tag" is required to download the data. (CLN = clean data)
+# kwargs = {"tag": 'CLN'}
+# For some events can specify channels: source data stream for LOSC data.
+# kwargs = {"channel": {'H1': 'H1:DCS-CALIB_STRAIN_C02',
+#                      'L1': 'L1:DCS-CALIB_STRAIN_C02',
+#                      'V1': 'V1:FAKE_h_16384Hz_4R'}}
+
+interferometers = bilby.gw.detector.get_event_data(
+    label, interferometer_names=interferometer_names,
+    duration=duration, roll_off=roll_off, psd_offset=psd_offset,
+    psd_duration=psd_duration, cache=True,
+    filter_freq=filter_freq, **kwargs)
+
+# CHOOSE PRIOR FILE
+# DEFAULT PRIOR FILES: GW150914.prior, binary_black_holes.prior,
+# binary_neutron_stars.prior
+# Needs to specify path for any other prior file.
+prior = bilby.gw.prior.BBHPriorDict(filename='GW150914.prior')
+
+# GENERATE WAVEFORM
+duration = None  # duration and sampling frequency will be overwritten
+# to match the ones in the interferometers.
+sampling_frequency = kwargs["sample_rate"]  # same at which the data is stored
+start_time = 0  # set the starting time of the time array
+
+# reference_frequency: either low freq. limit or most sensitive freq.
+# OVERVIEW OF APPROXIMANTS:
+# https://www.lsc-group.phys.uwm.edu/ligovirgo/cbcnote/Waveforms/Overview
+waveform_arguments = {'waveform_approximant': 'IMRPhenomPv2',
+                      'reference_frequency': 50}
+source_model = bilby.gw.source.lal_binary_black_hole
+
+waveform_generator = bilby.gw.WaveformGenerator(
+    duration=duration, sampling_frequency=sampling_frequency,
+    start_time=start_time,
+    frequency_domain_source_model=source_model,
+    waveform_arguments=waveform_arguments)
+
+# CHOOSE LIKELIHOOD FUNCTION
+# Time marginalisation uses FFT and can use a prior file.
+# Distance marginalisation uses a look up table calculated at run time.
+# Phase marginalisation is done analytically using a Bessel function.
+# If prior given, used in the distance and phase marginalization.
+likelihood = bilby.gw.likelihood.GravitationalWaveTransient(
+    interferometers, waveform_generator, time_marginalization=False,
+    distance_marginalization=False, phase_marginalization=False,
+    prior=None)
+
+# RUN SAMPLER
+# Can use log_likelihood_ratio, rather than just the log_likelihood.
+# If using simulated data, pass a dictionary of injection parameters.
+# A function can be specified in 'conversion_function' and applied
+# to posterior to generate additional parameters e.g. source-frame masses.
+
+# Implemented Samplers:
+# LIST OF AVAILABLE SAMPLERS: Run -> bilby.sampler.implemented_samplers
+npoints = 500  # number of live points for the MCMC (dynesty)
+sampler = 'dynesty'
+# Different samplers can have different additional kwargs,
+# visit https://lscsoft.docs.ligo.org/bilby/samplers.html for details.
+
+result = bilby.run_sampler(
+    likelihood, prior, outdir=outdir, label=label,
+    sampler=sampler, npoints=npoints, use_ratio=False,
+    injection_parameters=None,
+    conversion_function=bilby.gw.conversion.generate_all_bbh_parameters)
+
+result.plot_corner()