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# Matplotlib.pyplot.specgram() in Python

• Last Updated : 21 Apr, 2020

Matplotlib is a library in Python and it is numerical – mathematical extension for NumPy library. Pyplot is a state-based interface to a Matplotlib module which provides a MATLAB-like interface.

## matplotlib.pyplot.specgram() Function

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The specgram() function in pyplot module of matplotlib library is used to plot a spectrogram.

Syntax: matplotlib.pyplot.specgram(x, NFFT=None, Fs=None, Fc=None, detrend=None, window=None, noverlap=None, cmap=None, xextent=None, pad_to=None, sides=None, scale_by_freq=None, mode=None, scale=None, vmin=None, vmax=None, *, data=None, **kwargs)

Parameters: This method accept the following parameters that are described below:

• x: This parameter is a sequence of data.
• Fs : This parameter is a scalar. Its default value is 2.
• window: This parameter take a data segment as an argument and return the windowed version of the segment. Its default value is window_hanning()
• sides: This parameter specifies which sides of the spectrum to return. This can have following values : ‘default’, ‘onesided’ and ‘twosided’.
• pad_to : This parameter contains the integer value to which the data segment is padded.
• Fc: This parameter is also contains the integer value to offsets the x extents of the plot to reflect the frequency range. Its default value is 0
• NFFT : This parameter contains the number of data points used in each block for the FFT.
• detrend : This parameter contains the function applied to each segment before fft-ing, designed to remove the mean or linear trend {‘none’, ‘mean’, ‘linear’}.
• scale_by_freq : This parameter is allows for integration over the returned frequency values.
• mode : This parameter is that what sort of spectrum to use {‘default’, ‘psd’, ‘magnitude’, ‘angle’, ‘phase’}.
• noverlap : This parameter is the number of points of overlap between blocks.
• scale : This parameter contains the scaling of the values in the spec {‘default’, ‘linear’, ‘dB’}.
• Fc : This parameter is the center frequency of x.
• camp: This parameter is a matplotlib.colors.Colormap instance.

Returns: This returns the following:

• spectrum :This returns the angle spectrum in radians.
• freqs :This returns the frequencies corresponding to the elements in spectrum.
• t: This returns the times corresponding to midpoints of segments.
• im: This returns the image created by imshow containing the spectrogram.

The resultant is (spectrum, freqs, t, im)

Below examples illustrate the matplotlib.pyplot.specgram() function in matplotlib.pyplot:

Example 1:

 `# Implementation of matplotlib function``import` `matplotlib.pyplot as plt ``import` `numpy as np `` ` `   ` `dt ``=` `0.005``t ``=` `np.arange(``0.0``, ``20.0``, dt) ``x ``=` `np.sin(np.pi ``*` `t) ``+` `1.5` `*` `np.cos(np.pi ``*` `2``*``t) `` ` `plt.specgram(x, Fs ``=` `1``)``plt.title(``'matplotlib.pyplot.specgram() Example\n'``, ``          ``fontsize ``=` `14``, fontweight ``=``'bold'``)`` ` `plt.show()`

Output:

Example 2:

 `# Implementation of matplotlib function``import` `matplotlib.pyplot as plt ``import` `numpy as np `` ` ` ` `np.random.seed(``9360801``) ``   ` `dt ``=` `0.0005``t ``=` `np.arange(``0.0``, ``20.0``, dt) ``s1 ``=` `np.sin(``4` `*` `np.pi ``*` `100` `*` `t) ``s2 ``=` `1.5` `*` `np.sin(``1.5` `*` `np.pi ``*` `400` `*` `t) ``   ` `s2[t <``=` `10``] ``=` `s2[``12` `<``=` `t] ``=` `0``   ` `nse ``=` `0.2` `*` `np.random.random(size ``=` `len``(t)) ``   ` `x ``=` `s1 ``+` `s2 ``+` `nse   ``NFFT ``=` `512` `Fs ``=` `int``(``1.0` `/` `dt)  `` ` `plt.specgram(x, Fs ``=` `Fs, cmap ``=` `plt.cm.bone) ``plt.title(``'matplotlib.pyplot.specgram() Example\n'``,``          ``fontsize ``=` `14``, fontweight ``=``'bold'``)`` ` `plt.show()`

Output:

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