.. sectionauthor:: Duncan Macleod <duncan.macleod@ligo.org>

.. currentmodule:: gwpy.table.lsctables

Plotting an event histogram
###########################

I would like to study the snr distribution of event triggers generated by
the ExcessPower gravitational-wave burst detection algorithm,
over a small stretch of data.

The data from which these events were generated are a simulation of Gaussian
noise with the Advanced LIGO design spectrum, and so don't actually contain
any real gravitational waves, but will help tune the algorithm to improve
detection of future, real signals.



First, we import the `SnglBurstTable`, an XML-based data holder for single-detector ('Sngl') gravitational-wave burst-like events:

.. code-block:: python

   from gwpy.table.lsctables import SnglBurstTable


We can read a set of events using the :meth:`~SnglBurstTable.read` method:

.. code-block:: python

   events = SnglBurstTable.read('../../gwpy/tests/data/H1-LDAS_STRAIN-968654552-10.xml.gz')


and can generate a new `~gwpy.plotter.HistogramPlot` using the :meth:`~SnglBurstTable.hist` instance method

.. code-block:: python

   plot = events.hist('snr', weights=1/10., log=True, logbins=True, histtype='stepfilled', cumulative=-1)
   plot.set_xlabel('Signal-to-noise ratio (SNR)')
   plot.set_ylabel('Rate [Hz]')
   plot.set_title('LHO event triggers for GW100916')
   plot.show()

.. plot:: ../examples/table/histogram.py