.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "examples/frequencyseries/inject-fs.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_examples_frequencyseries_inject-fs.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_examples_frequencyseries_inject-fs.py:


.. currentmodule:: gwpy.timeseries
.. sectionauthor:: Alex Urban <alexander.urban@ligo.org>

Inject a signal into a `FrequencySeries`
########################################

It can often be useful to add some known signal to inherently random
or noisy data. For example, one might want to investigate what
would happen if a binary black hole merger signal occured at or near
the time of a glitch. In LIGO data analysis, this procedure is referred
to as an *injection*.

In the example below we will create a stream of random, white Gaussian
noise, then inject a loud, steady sinuosoid. We will do this in the
frequency domain because it is much easier to model a sinusoid there.

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Generate random data
--------------------
First, we prepare one second of Gaussian noise using
`numpy.random.Generator.normal`:

.. GENERATED FROM PYTHON SOURCE LINES 42-48

.. code-block:: Python


    from numpy.random import default_rng
    from gwpy.timeseries import TimeSeries
    rng = default_rng()
    noise = TimeSeries(rng.normal(scale=.1, size=1024), sample_rate=1024)








.. GENERATED FROM PYTHON SOURCE LINES 49-50

To inject a signal in the frequency domain, we need to take an FFT:

.. GENERATED FROM PYTHON SOURCE LINES 50-53

.. code-block:: Python


    noisefd = noise.fft()








.. GENERATED FROM PYTHON SOURCE LINES 54-59

Inject noise
------------
We can now easily inject a loud sinusoid of unit amplitude at, say,
30 Hz. To do this, we use
:meth:`~gwpy.frequencyseries.FrequencySeries.inject`:

.. GENERATED FROM PYTHON SOURCE LINES 59-65

.. code-block:: Python


    import numpy
    from gwpy.frequencyseries import FrequencySeries
    signal = FrequencySeries(numpy.array([1.]), f0=30, df=noisefd.df)
    injfd = noisefd.inject(signal)








.. GENERATED FROM PYTHON SOURCE LINES 66-70

Visualisation
-------------
We can then visualize the data before and after injection in the frequency
domain:

.. GENERATED FROM PYTHON SOURCE LINES 70-80

.. code-block:: Python


    from gwpy.plot import Plot
    plot = Plot(
        numpy.abs(noisefd),
        numpy.abs(injfd),
        xscale="log",
        yscale="log",
    )
    plot.show()




.. image-sg:: /examples/frequencyseries/images/sphx_glr_inject-fs_001.png
   :alt: inject fs
   :srcset: /examples/frequencyseries/images/sphx_glr_inject-fs_001.png
   :class: sphx-glr-single-img





.. GENERATED FROM PYTHON SOURCE LINES 81-83

Finally, for completeness we can visualize the effect before and after
injection back in the time domain:

.. GENERATED FROM PYTHON SOURCE LINES 83-94

.. code-block:: Python


    inj = injfd.ifft()
    plot = Plot(
        noise,
        inj,
        separate=True,
        sharex=True,
        sharey=True,
        figsize=(12, 6),
    )
    plot.show()



.. image-sg:: /examples/frequencyseries/images/sphx_glr_inject-fs_002.png
   :alt: inject fs
   :srcset: /examples/frequencyseries/images/sphx_glr_inject-fs_002.png
   :class: sphx-glr-single-img






.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 0.631 seconds)


.. _sphx_glr_download_examples_frequencyseries_inject-fs.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: inject-fs.ipynb <inject-fs.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: inject-fs.py <inject-fs.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: inject-fs.zip <inject-fs.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_