.. _gwpy-example-frequencyseries-hoff:

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

.. currentmodule:: gwpy.frequencyseries

Calculating and plotting a `FrequencySeries`
############################################

The LIGO Laboratory has publicly released the strain data around the time of
the GW150914 gravitational-wave detection; we can use these to calculate
and display the spectral sensitivity of each of the detectors at that time.

In order to generate a `FrequencySeries` we need to import the
`~gwpy.timeseries.TimeSeries` and use
:meth:`~gwpy.timeseries.TimeSeries.fetch_open_data` to download the strain
records:


.. plot::
   :context: reset
   :nofigs:
   :include-source:

   from gwpy.timeseries import TimeSeries
   lho = TimeSeries.fetch_open_data('H1', 1126259446, 1126259478)
   llo = TimeSeries.fetch_open_data('L1', 1126259446, 1126259478)

We can then call the :meth:`~gwpy.timeseries.TimeSeries.asd` method to
calculated the amplitude spectral density for each
`~gwpy.timeseries.TimeSeries`:

.. plot::
   :context:
   :nofigs:
   :include-source:

   lhoasd = lho.asd(4, 2)
   lloasd = llo.asd(4, 2)

We can then :meth:`~FrequencySeries.plot` the spectra using the 'standard'
colour scheme:

.. plot::
   :context:
   :include-source:

   plot = lhoasd.plot(label='LIGO-Hanford', color='gwpy:ligo-hanford')
   ax = plot.gca()
   ax.plot(lloasd, label='LIGO-Livingston', color='gwpy:ligo-livingston')
   ax.set_xlim(10, 2000)
   ax.set_ylim(5e-24, 1e-21)
   ax.legend(frameon=False, bbox_to_anchor=(1., 1.), loc='lower right', ncol=2)
   plot.show()