.. only:: html .. note:: :class: sphx-glr-download-link-note Click :ref:`here ` to download the full example code .. rst-class:: sphx-glr-example-title .. _sphx_glr_gallery_images_contours_and_fields_specgram_demo.py: ================ Spectrogram Demo ================ Demo of a spectrogram plot (`~.axes.Axes.specgram`). .. code-block:: default import matplotlib.pyplot as plt import numpy as np # Fixing random state for reproducibility np.random.seed(19680801) dt = 0.0005 t = np.arange(0.0, 20.0, dt) s1 = np.sin(2 * np.pi * 100 * t) s2 = 2 * np.sin(2 * np.pi * 400 * t) # create a transient "chirp" s2[t <= 10] = s2[12 <= t] = 0 # add some noise into the mix nse = 0.01 * np.random.random(size=len(t)) x = s1 + s2 + nse # the signal NFFT = 1024 # the length of the windowing segments Fs = int(1.0 / dt) # the sampling frequency fig, (ax1, ax2) = plt.subplots(nrows=2) ax1.plot(t, x) Pxx, freqs, bins, im = ax2.specgram(x, NFFT=NFFT, Fs=Fs, noverlap=900) # The `specgram` method returns 4 objects. They are: # - Pxx: the periodogram # - freqs: the frequency vector # - bins: the centers of the time bins # - im: the .image.AxesImage instance representing the data in the plot plt.show() .. image:: /gallery/images_contours_and_fields/images/sphx_glr_specgram_demo_001.png :alt: specgram demo :class: sphx-glr-single-img ------------ References """""""""" The use of the following functions, methods is shown in this example: .. code-block:: default import matplotlib matplotlib.axes.Axes.specgram matplotlib.pyplot.specgram .. rst-class:: sphx-glr-script-out Out: .. code-block:: none .. _sphx_glr_download_gallery_images_contours_and_fields_specgram_demo.py: .. only :: html .. container:: sphx-glr-footer :class: sphx-glr-footer-example .. container:: sphx-glr-download sphx-glr-download-python :download:`Download Python source code: specgram_demo.py ` .. container:: sphx-glr-download sphx-glr-download-jupyter :download:`Download Jupyter notebook: specgram_demo.ipynb ` .. only:: html .. rst-class:: sphx-glr-signature Keywords: matplotlib code example, codex, python plot, pyplot `Gallery generated by Sphinx-Gallery `_