.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "intro/scipy/auto_examples/plot_spectrogram.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

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

        :ref:`Go to the end <sphx_glr_download_intro_scipy_auto_examples_plot_spectrogram.py>`
        to download the full example code

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

.. _sphx_glr_intro_scipy_auto_examples_plot_spectrogram.py:


======================================
Spectrogram, power spectral density
======================================

Demo spectrogram and power spectral density on a frequency chirp.

.. GENERATED FROM PYTHON SOURCE LINES 8-12

.. code-block:: default


    import numpy as np
    import matplotlib.pyplot as plt








.. GENERATED FROM PYTHON SOURCE LINES 13-15

Generate a chirp signal
###########################################################

.. GENERATED FROM PYTHON SOURCE LINES 15-28

.. code-block:: default


    # Seed the random number generator
    np.random.seed(0)

    time_step = .01
    time_vec = np.arange(0, 70, time_step)

    # A signal with a small frequency chirp
    sig = np.sin(0.5 * np.pi * time_vec * (1 + .1 * time_vec))

    plt.figure(figsize=(8, 5))
    plt.plot(time_vec, sig)




.. image-sg:: /intro/scipy/auto_examples/images/sphx_glr_plot_spectrogram_001.png
   :alt: plot spectrogram
   :srcset: /intro/scipy/auto_examples/images/sphx_glr_plot_spectrogram_001.png
   :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 .. code-block:: none


    [<matplotlib.lines.Line2D object at 0x7fe7b04e1310>]



.. GENERATED FROM PYTHON SOURCE LINES 29-33

Compute and plot the spectrogram
###########################################################

 The spectrum of the signal on consecutive time windows

.. GENERATED FROM PYTHON SOURCE LINES 33-45

.. code-block:: default


    import scipy as sp
    freqs, times, spectrogram = sp.signal.spectrogram(sig)

    plt.figure(figsize=(5, 4))
    plt.imshow(spectrogram, aspect='auto', cmap='hot_r', origin='lower')
    plt.title('Spectrogram')
    plt.ylabel('Frequency band')
    plt.xlabel('Time window')
    plt.tight_layout()





.. image-sg:: /intro/scipy/auto_examples/images/sphx_glr_plot_spectrogram_002.png
   :alt: Spectrogram
   :srcset: /intro/scipy/auto_examples/images/sphx_glr_plot_spectrogram_002.png
   :class: sphx-glr-single-img





.. GENERATED FROM PYTHON SOURCE LINES 46-50

Compute and plot the power spectral density (PSD)
###########################################################

 The power of the signal per frequency band

.. GENERATED FROM PYTHON SOURCE LINES 50-60

.. code-block:: default


    freqs, psd = sp.signal.welch(sig)

    plt.figure(figsize=(5, 4))
    plt.semilogx(freqs, psd)
    plt.title('PSD: power spectral density')
    plt.xlabel('Frequency')
    plt.ylabel('Power')
    plt.tight_layout()




.. image-sg:: /intro/scipy/auto_examples/images/sphx_glr_plot_spectrogram_003.png
   :alt: PSD: power spectral density
   :srcset: /intro/scipy/auto_examples/images/sphx_glr_plot_spectrogram_003.png
   :class: sphx-glr-single-img





.. GENERATED FROM PYTHON SOURCE LINES 61-63

.. code-block:: default


    plt.show()








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

   **Total running time of the script:** ( 0 minutes  0.273 seconds)


.. _sphx_glr_download_intro_scipy_auto_examples_plot_spectrogram.py:

.. only:: html

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




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

      :download:`Download Python source code: plot_spectrogram.py <plot_spectrogram.py>`

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

      :download:`Download Jupyter notebook: plot_spectrogram.ipynb <plot_spectrogram.ipynb>`


.. only:: html

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

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