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

.. currentmodule:: gwpy.frequencyseries

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

I'm interested in the level of ground motion surrounding a particular time
during commissioning of the Advanced LIGO Livingston Observatory. I don't
have access to the frame files on disk, so I'll need to use NDS.



In order to generate a `FrequencySeries` we need to import the
`~gwpy.timeseries.TimeSeries` and :meth:`~gwpy.timeseries.TimeSeries.get`
the data:

.. code-block:: python

   from gwpy.timeseries import TimeSeries
   lho = TimeSeries.get(
       'H1:LDAS-STRAIN,rds', 'August 1 2010', 'August 1 2010 00:02')
   llo = TimeSeries.get(
       'L1:LDAS-STRAIN,rds', 'August 1 2010', 'August 1 2010 00:02')


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

.. code-block:: python

   lhoasd = lho.asd(2, 1)
   lloasd = llo.asd(2, 1)


We can then :meth:`~FrequencySeries.plot` the spectra

.. code-block:: python

   plot = lhoasd.plot(color='b', label='LHO')
   ax = plot.gca()
   ax.plot(lloasd, color='g', label='LLO')
   ax.set_xlim(40, 4096)
   ax.set_ylim(1e-23, 7.5e-21)
   ax.spines['right'].set_visible(False)
   ax.spines['top'].set_visible(False)
   ax.get_xaxis().tick_bottom()
   ax.get_yaxis().tick_right()
   plot.show()

.. plot:: ../examples/frequencyseries/hoff.py