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

.. currentmodule:: gwpy.plotter

Plotting a filter
#################

I would like to look at the Bode representation of a linear filter.



First, we import the objects we need

.. code-block:: python

   from math import pi
   from scipy import signal
   from gwpy.plotter import BodePlot


Now, we can calculate a fourth-order butterworth filter using the
:meth:`~scipy.signal.butter` function

.. code-block:: python

   highpass = signal.butter(4, 10 * (2. * pi), btype='highpass',
                            analog=True)


The `BodePlot` knows how to plot filters:

.. code-block:: python

   plot = BodePlot(highpass)
   plot.maxes.set_title('10\,Hz high-pass filter (4th order Butterworth)')
   plot.show()

.. plot:: ../examples/miscellaneous/bode_plot.py