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Editing: _windows.cpython-311.pyc
� d�c�F � �� � d Z ddlZddlZddlZddlmZmZmZ g d�Z d� Z d� Z d� Z d=d �Zd=d �Zd=d �Zd=d �Zd=d �Zd=d�Zd=d�Zd=d�Zd=d�Zd=d�Zd=d�Zd>d�Zd=d�Zd=d�Zd=d�Z d=d�Z dd�d�Z d=d �Z d=d �Z d=d �Z!d=d �Z"d?d!�Z#d@d$�Z$dAd&�Z%dd�d'�Z&d(� Z'i d)ed%f�d*ed%f�d+ed%f�d,ed%f�d-ed%f�d.ed%f�d/e!df�d0e"d%f�d1e%df�d2e#d%f�d3ed%f�d4e df�d5edf�d6e df�d7edf�d8e d%f�d9ed%f�e dfe dfe&d%fed%fed%fe$d%fed%fed%fd:��Z(i Z)e(�* � � D ]\ Z+Z,e+D ] Z-e,d e)e-< �� e.� � Z/e(�* � � D ]"\ Z+Z,e,d; re/�0 e+� � �#d=d<�Z1dS )Bz The suite of window functions.� N)�linalg�special�fft)�boxcar�triang�parzen�bohman�blackman�nuttall�blackmanharris�flattop�bartlett�barthann�hamming�kaiser�kaiser_bessel_derived�gaussian�general_cosine�general_gaussian�general_hamming�chebwin�cosine�hann� exponential�tukey�taylor�dpss� get_window�lanczosc �^ � t | � � | k s| dk rt d� � �| dk S )z(Handle small or incorrect window lengthsr z.Window length M must be a non-negative integer� )�int� ValueError)�Ms �?/usr/lib/python3/dist-packages/scipy/signal/windows/_windows.py� _len_guardsr& s1 � � �1�v�v��{�{�a�!�e�e��I�J�J�J� ��6�M� c � � |s| dz dfS | dfS )z9Extend window by 1 sample if needed for DFT-even symmetryr! TF� �r$ �syms r% �_extendr, s! � � � ��1�u�d�{���%�x�r' c � � |r | dd� S | S )z;Truncate window by 1 sample if needed for DFT-even symmetryN���r) )�w�neededs r% � _truncater1 s � � � ���"��v� ��r' Tc � � t | � � rt j | � � S t | |� � \ } }t j t j t j | � � }t j | � � }t t |� � � � D ]%}||| t j ||z � � z z }�&t ||� � S )a� Generic weighted sum of cosine terms window Parameters ---------- M : int Number of points in the output window a : array_like Sequence of weighting coefficients. This uses the convention of being centered on the origin, so these will typically all be positive numbers, not alternating sign. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The array of window values. References ---------- .. [1] A. Nuttall, "Some windows with very good sidelobe behavior," IEEE Transactions on Acoustics, Speech, and Signal Processing, vol. 29, no. 1, pp. 84-91, Feb 1981. :doi:`10.1109/TASSP.1981.1163506`. .. [2] Heinzel G. et al., "Spectrum and spectral density estimation by the Discrete Fourier transform (DFT), including a comprehensive list of window functions and some new flat-top windows", February 15, 2002 https://holometer.fnal.gov/GH_FFT.pdf Examples -------- Heinzel describes a flat-top window named "HFT90D" with formula: [2]_ .. math:: w_j = 1 - 1.942604 \cos(z) + 1.340318 \cos(2z) - 0.440811 \cos(3z) + 0.043097 \cos(4z) where .. math:: z = \frac{2 \pi j}{N}, j = 0...N - 1 Since this uses the convention of starting at the origin, to reproduce the window, we need to convert every other coefficient to a positive number: >>> HFT90D = [1, 1.942604, 1.340318, 0.440811, 0.043097] The paper states that the highest sidelobe is at -90.2 dB. Reproduce Figure 42 by plotting the window and its frequency response, and confirm the sidelobe level in red: >>> import numpy as np >>> from scipy.signal.windows import general_cosine >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = general_cosine(1000, HFT90D, sym=False) >>> plt.plot(window) >>> plt.title("HFT90D window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 10000) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = np.abs(fftshift(A / abs(A).max())) >>> response = 20 * np.log10(np.maximum(response, 1e-10)) >>> plt.plot(freq, response) >>> plt.axis([-50/1000, 50/1000, -140, 0]) >>> plt.title("Frequency response of the HFT90D window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") >>> plt.axhline(-90.2, color='red') >>> plt.show() ) r& �np�onesr, �linspace�pi�zeros�range�len�cosr1 )r$ �ar+ � needs_trunc�facr/ �ks r% r r ( s� � �X �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� �+�r�u�f�b�e�Q� '� '�C� ��� � �A� �3�q�6�6�]�]� $� $�� �Q�q�T�B�F�1�s�7�O�O� #�#��� �Q� � $� $�$r' c �� � t | � � rt j | � � S t | |� � \ } }t j | t � � }t ||� � S )a; Return a boxcar or rectangular window. Also known as a rectangular window or Dirichlet window, this is equivalent to no window at all. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional Whether the window is symmetric. (Has no effect for boxcar.) Returns ------- w : ndarray The window, with the maximum value normalized to 1. Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.boxcar(51) >>> plt.plot(window) >>> plt.title("Boxcar window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the boxcar window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") )r& r3 r4 r, �floatr1 �r$ r+ r< r/ s r% r r � sS � �Z �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� ���5���A� �Q� � $� $�$r' c �~ � t | � � rt j | � � S t | |� � \ } }t j d| dz dz dz � � }| dz dk r)d|z dz | z }t j ||ddd� f }n(d|z | dz z }t j ||ddd� f }t ||� � S )a Return a triangular window. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). See Also -------- bartlett : A triangular window that touches zero Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.triang(51) >>> plt.plot(window) >>> plt.title("Triangular window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = np.abs(fftshift(A / abs(A).max())) >>> response = 20 * np.log10(np.maximum(response, 1e-10)) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the triangular window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") r! � r � �?Nr. ���)r& r3 r4 r, �arange�r_r1 �r$ r+ r< �nr/ s r% r r � s� � �d �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� � �!�a�!�e��\�A�%�&�&�A��1�u��z�z� ��U�S�[�A� �� �E�!�Q�t�t��t�W�*� ��� ��E�Q��W� �� �E�!�Q�r�v�2�v�Y�,� �� �Q� � $� $�$r' c �| � t | � � rt j | � � S t | |� � \ } }t j | dz dz | dz dz dz d� � }t j || dz dz k |� � }t j t |� � | dz dz k |� � }ddt j |� � | dz z z dz z }ddt j |� � | dz z dz z z dt j |� � | dz z dz z z }t j |||d d d � f }t ||� � S ) a+ Return a Parzen window. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). References ---------- .. [1] E. Parzen, "Mathematical Considerations in the Estimation of Spectra", Technometrics, Vol. 3, No. 2 (May, 1961), pp. 167-190 Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.parzen(51) >>> plt.plot(window) >>> plt.title("Parzen window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the Parzen window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") r! � @� �?rD g @rC g @� Nr. ) r& r3 r4 r, rF �extract�absrG r1 ) r$ r+ r< rI �na�nb�wa�wbr/ s r% r r � s: � �d �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� � �A��E�(�S�.�1�q�5�C�-�#�"5�s�;�;�A� ��A�!�a�%��3��&�� *� *�B� ��C��F�F�q�1�u��m�+�Q� /� /�B� �a�"�&��*�*��C��(�(�S� 0� 0�B� �a�2�6�"�:�:��S��)�c�1�1� 1� �r�v�b�z�z�Q��W�%�#�-� -� .�B� ��b�"�b���2��h� � �A� �Q� � $� $�$r' c �� � t | � � rt j | � � S t | |� � \ } }t j t j dd| � � dd� � � }d|z t j t j |z � � z dt j z t j t j |z � � z z }t j d|df }t ||� � S )ax Return a Bohman window. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.bohman(51) >>> plt.plot(window) >>> plt.title("Bohman window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the Bohman window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") r. r! rD r ) r& r3 r4 r, rO r5 r: r6 �sinrG r1 )r$ r+ r< r= r/ s r% r r 8 s� � �Z �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� �&���R��A�&�&�q��t�,� -� -�C� �S��B�F�2�5�3�;�'�'�'�#���+���r�u�s�{�8K�8K�*K�K�A� ��a��A�g��A� �Q� � $� $�$r' c �( � t | g d�|� � S )ah Return a Blackman window. The Blackman window is a taper formed by using the first three terms of a summation of cosines. It was designed to have close to the minimal leakage possible. It is close to optimal, only slightly worse than a Kaiser window. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). Notes ----- The Blackman window is defined as .. math:: w(n) = 0.42 - 0.5 \cos(2\pi n/M) + 0.08 \cos(4\pi n/M) The "exact Blackman" window was designed to null out the third and fourth sidelobes, but has discontinuities at the boundaries, resulting in a 6 dB/oct fall-off. This window is an approximation of the "exact" window, which does not null the sidelobes as well, but is smooth at the edges, improving the fall-off rate to 18 dB/oct. [3]_ Most references to the Blackman window come from the signal processing literature, where it is used as one of many windowing functions for smoothing values. It is also known as an apodization (which means "removing the foot", i.e. smoothing discontinuities at the beginning and end of the sampled signal) or tapering function. It is known as a "near optimal" tapering function, almost as good (by some measures) as the Kaiser window. References ---------- .. [1] Blackman, R.B. and Tukey, J.W., (1958) The measurement of power spectra, Dover Publications, New York. .. [2] Oppenheim, A.V., and R.W. Schafer. Discrete-Time Signal Processing. Upper Saddle River, NJ: Prentice-Hall, 1999, pp. 468-471. .. [3] Harris, Fredric J. (Jan 1978). "On the use of Windows for Harmonic Analysis with the Discrete Fourier Transform". Proceedings of the IEEE 66 (1): 51-83. :doi:`10.1109/PROC.1978.10837`. Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.blackman(51) >>> plt.plot(window) >>> plt.title("Blackman window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = np.abs(fftshift(A / abs(A).max())) >>> response = 20 * np.log10(np.maximum(response, 1e-10)) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the Blackman window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") )g�z�G��?rL g{�G�z�?�r r* s r% r r p s � �f �!� /� /� /�� 5� 5�5r' c �( � t | g d�|� � S )a Return a minimum 4-term Blackman-Harris window according to Nuttall. This variation is called "Nuttall4c" by Heinzel. [2]_ Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). References ---------- .. [1] A. Nuttall, "Some windows with very good sidelobe behavior," IEEE Transactions on Acoustics, Speech, and Signal Processing, vol. 29, no. 1, pp. 84-91, Feb 1981. :doi:`10.1109/TASSP.1981.1163506`. .. [2] Heinzel G. et al., "Spectrum and spectral density estimation by the Discrete Fourier transform (DFT), including a comprehensive list of window functions and some new flat-top windows", February 15, 2002 https://holometer.fnal.gov/GH_FFT.pdf Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.nuttall(51) >>> plt.plot(window) >>> plt.title("Nuttall window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the Nuttall window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") )g�z�D�?g; %�N�?g�1��|�?g��C ˅?rW r* s r% r r � s � �r �!� I� I� I�3� O� O�Or' c �( � t | g d�|� � S )a� Return a minimum 4-term Blackman-Harris window. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.blackmanharris(51) >>> plt.plot(window) >>> plt.title("Blackman-Harris window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the Blackman-Harris window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") )g�(\���?g��=�$@�?g�ʉv�?g�c#��?rW r* s r% r r s � �Z �!� A� A� A�3� G� G�Gr' c �, � g d�}t | ||� � S )a� Return a flat top window. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). Notes ----- Flat top windows are used for taking accurate measurements of signal amplitude in the frequency domain, with minimal scalloping error from the center of a frequency bin to its edges, compared to others. This is a 5th-order cosine window, with the 5 terms optimized to make the main lobe maximally flat. [1]_ References ---------- .. [1] D'Antona, Gabriele, and A. Ferrero, "Digital Signal Processing for Measurement Systems", Springer Media, 2006, p. 70 :doi:`10.1007/0-387-28666-7`. Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.flattop(51) >>> plt.plot(window) >>> plt.title("Flat top window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the flat top window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") )g�^�M��?g�+����?g<������?g'� ne�?g����t|?rW )r$ r+ r; s r% r r 2 s# � �v H�G�G�A� �!�Q�� $� $�$r' c �@ � t | � � rt j | � � S t | |� � \ } }t j d| � � }t j t j || dz dz � � d|z | dz z dd|z | dz z z � � }t ||� � S )a� Return a Bartlett window. The Bartlett window is very similar to a triangular window, except that the end points are at zero. It is often used in signal processing for tapering a signal, without generating too much ripple in the frequency domain. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The triangular window, with the first and last samples equal to zero and the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). See Also -------- triang : A triangular window that does not touch zero at the ends Notes ----- The Bartlett window is defined as .. math:: w(n) = \frac{2}{M-1} \left( \frac{M-1}{2} - \left|n - \frac{M-1}{2}\right| \right) Most references to the Bartlett window come from the signal processing literature, where it is used as one of many windowing functions for smoothing values. Note that convolution with this window produces linear interpolation. It is also known as an apodization (which means"removing the foot", i.e. smoothing discontinuities at the beginning and end of the sampled signal) or tapering function. The Fourier transform of the Bartlett is the product of two sinc functions. Note the excellent discussion in Kanasewich. [2]_ References ---------- .. [1] M.S. Bartlett, "Periodogram Analysis and Continuous Spectra", Biometrika 37, 1-16, 1950. .. [2] E.R. Kanasewich, "Time Sequence Analysis in Geophysics", The University of Alberta Press, 1975, pp. 109-110. .. [3] A.V. Oppenheim and R.W. Schafer, "Discrete-Time Signal Processing", Prentice-Hall, 1999, pp. 468-471. .. [4] Wikipedia, "Window function", https://en.wikipedia.org/wiki/Window_function .. [5] W.H. Press, B.P. Flannery, S.A. Teukolsky, and W.T. Vetterling, "Numerical Recipes", Cambridge University Press, 1986, page 429. Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.bartlett(51) >>> plt.plot(window) >>> plt.title("Bartlett window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the Bartlett window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") r r! rK )r& r3 r4 r, rF �where� less_equalr1 rH s r% r r q s� � �p �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� � �!�Q���A� ��� �q�1�q�5�C�-�0�0��q��A��E�"�C�#��'�Q��U�*;�$;� =� =�A� �Q� � $� $�$r' c �$ � t | d|� � S )aQ Return a Hann window. The Hann window is a taper formed by using a raised cosine or sine-squared with ends that touch zero. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). Notes ----- The Hann window is defined as .. math:: w(n) = 0.5 - 0.5 \cos\left(\frac{2\pi{n}}{M-1}\right) \qquad 0 \leq n \leq M-1 The window was named for Julius von Hann, an Austrian meteorologist. It is also known as the Cosine Bell. It is sometimes erroneously referred to as the "Hanning" window, from the use of "hann" as a verb in the original paper and confusion with the very similar Hamming window. Most references to the Hann window come from the signal processing literature, where it is used as one of many windowing functions for smoothing values. It is also known as an apodization (which means "removing the foot", i.e. smoothing discontinuities at the beginning and end of the sampled signal) or tapering function. References ---------- .. [1] Blackman, R.B. and Tukey, J.W., (1958) The measurement of power spectra, Dover Publications, New York. .. [2] E.R. Kanasewich, "Time Sequence Analysis in Geophysics", The University of Alberta Press, 1975, pp. 106-108. .. [3] Wikipedia, "Window function", https://en.wikipedia.org/wiki/Window_function .. [4] W.H. Press, B.P. Flannery, S.A. Teukolsky, and W.T. Vetterling, "Numerical Recipes", Cambridge University Press, 1986, page 425. Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.hann(51) >>> plt.plot(window) >>> plt.title("Hann window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = np.abs(fftshift(A / abs(A).max())) >>> response = 20 * np.log10(np.maximum(response, 1e-10)) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the Hann window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") rL �r r* s r% r r � s � �` �1�c�3� '� '�'r' rL c � � t | � � rt j | � � S |dk rt j | d� � S |dk rt | |�� � S t | |� � \ } }t j d| � � }t t j || dz z dz � � � � }|d|dz � }||dz | |z dz � }|| |z dz d� }ddt j t j d d|z |z | dz z z z � � z z } t j |j � � } ddt j t j d |z dz d|z |z | dz z z z � � z z } t j | | | f� � } t | |� � S ) aB Return a Tukey window, also known as a tapered cosine window. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. alpha : float, optional Shape parameter of the Tukey window, representing the fraction of the window inside the cosine tapered region. If zero, the Tukey window is equivalent to a rectangular window. If one, the Tukey window is equivalent to a Hann window. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). References ---------- .. [1] Harris, Fredric J. (Jan 1978). "On the use of Windows for Harmonic Analysis with the Discrete Fourier Transform". Proceedings of the IEEE 66 (1): 51-83. :doi:`10.1109/PROC.1978.10837` .. [2] Wikipedia, "Window function", https://en.wikipedia.org/wiki/Window_function#Tukey_window Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.tukey(51) >>> plt.plot(window) >>> plt.title("Tukey window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.ylim([0, 1.1]) >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the Tukey window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") r �drD �r+ r! rK NrL r. g �) r& r3 r4 r r, rF r" �floorr: r6 �shape� concatenater1 ) r$ �alphar+ r< rI �width�n1�n2�n3�w1�w2�w3r/ s r% r r ' s� � �v �1�~�~� ��w�q�z�z�� ��z�z��w�q�#��� � �#� � ��A�3� � � � � �Q��_�_�N�A�{� � �!�Q���A� �����!���S� �)�)� *� *�E� �1�U�1�W�9� �B� �5��7�1�U�7�1�9� � �B� �1�U�7�1�9�:�:� �B� ��B�F�2�5�B��R��� �q��s�);�$;�<�=�=�=� >�B� ���� � �B� ��B�F�2�5�D��J��N�S��V�E�\�1�Q�3�5G�$G�H�I�I�I� J�B� ���B��|�$�$�A� �Q� � $� $�$r' c �R � t | � � rt j | � � S t | |� � \ } }t j d| � � }t j || dz z dz � � }dd|z z dt j dt j z |z � � z z }t ||� � S )a� Return a modified Bartlett-Hann window. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.barthann(51) >>> plt.plot(window) >>> plt.title("Bartlett-Hann window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the Bartlett-Hann window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") r rD rL gףp= ��?g� ��Q��?gR� ��Q�?rC ) r& r3 r4 r, rF rO r: r6 r1 )r$ r+ r< rI r= r/ s r% r r { s� � �Z �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� � �!�Q���A� �&��a�#�g� ��$� %� %�C� �t�c�z��D�2�6�!�b�e�)�c�/�#:�#:� :�:�A� �Q� � $� $�$r' c �. � t | |d|z g|� � S )aA Return a generalized Hamming window. The generalized Hamming window is constructed by multiplying a rectangular window by one period of a cosine function [1]_. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. alpha : float The window coefficient, :math:`\alpha` sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). See Also -------- hamming, hann Notes ----- The generalized Hamming window is defined as .. math:: w(n) = \alpha - \left(1 - \alpha\right) \cos\left(\frac{2\pi{n}}{M-1}\right) \qquad 0 \leq n \leq M-1 Both the common Hamming window and Hann window are special cases of the generalized Hamming window with :math:`\alpha` = 0.54 and :math:`\alpha` = 0.5, respectively [2]_. References ---------- .. [1] DSPRelated, "Generalized Hamming Window Family", https://www.dsprelated.com/freebooks/sasp/Generalized_Hamming_Window_Family.html .. [2] Wikipedia, "Window function", https://en.wikipedia.org/wiki/Window_function .. [3] Riccardo Piantanida ESA, "Sentinel-1 Level 1 Detailed Algorithm Definition", https://sentinel.esa.int/documents/247904/1877131/Sentinel-1-Level-1-Detailed-Algorithm-Definition .. [4] Matthieu Bourbigot ESA, "Sentinel-1 Product Definition", https://sentinel.esa.int/documents/247904/1877131/Sentinel-1-Product-Definition Examples -------- The Sentinel-1A/B Instrument Processing Facility uses generalized Hamming windows in the processing of spaceborne Synthetic Aperture Radar (SAR) data [3]_. The facility uses various values for the :math:`\alpha` parameter based on operating mode of the SAR instrument. Some common :math:`\alpha` values include 0.75, 0.7 and 0.52 [4]_. As an example, we plot these different windows. >>> import numpy as np >>> from scipy.signal.windows import general_hamming >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> fig1, spatial_plot = plt.subplots() >>> spatial_plot.set_title("Generalized Hamming Windows") >>> spatial_plot.set_ylabel("Amplitude") >>> spatial_plot.set_xlabel("Sample") >>> fig2, freq_plot = plt.subplots() >>> freq_plot.set_title("Frequency Responses") >>> freq_plot.set_ylabel("Normalized magnitude [dB]") >>> freq_plot.set_xlabel("Normalized frequency [cycles per sample]") >>> for alpha in [0.75, 0.7, 0.52]: ... window = general_hamming(41, alpha) ... spatial_plot.plot(window, label="{:.2f}".format(alpha)) ... A = fft(window, 2048) / (len(window)/2.0) ... freq = np.linspace(-0.5, 0.5, len(A)) ... response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) ... freq_plot.plot(freq, response, label="{:.2f}".format(alpha)) >>> freq_plot.legend(loc="upper right") >>> spatial_plot.legend(loc="upper right") rD rW )r$ rf r+ s r% r r � s � �l �!�e�R�%�Z� 0�#� 6� 6�6r' c �$ � t | d|� � S )a� Return a Hamming window. The Hamming window is a taper formed by using a raised cosine with non-zero endpoints, optimized to minimize the nearest side lobe. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). Notes ----- The Hamming window is defined as .. math:: w(n) = 0.54 - 0.46 \cos\left(\frac{2\pi{n}}{M-1}\right) \qquad 0 \leq n \leq M-1 The Hamming was named for R. W. Hamming, an associate of J. W. Tukey and is described in Blackman and Tukey. It was recommended for smoothing the truncated autocovariance function in the time domain. Most references to the Hamming window come from the signal processing literature, where it is used as one of many windowing functions for smoothing values. It is also known as an apodization (which means "removing the foot", i.e. smoothing discontinuities at the beginning and end of the sampled signal) or tapering function. References ---------- .. [1] Blackman, R.B. and Tukey, J.W., (1958) The measurement of power spectra, Dover Publications, New York. .. [2] E.R. Kanasewich, "Time Sequence Analysis in Geophysics", The University of Alberta Press, 1975, pp. 109-110. .. [3] Wikipedia, "Window function", https://en.wikipedia.org/wiki/Window_function .. [4] W.H. Press, B.P. Flannery, S.A. Teukolsky, and W.T. Vetterling, "Numerical Recipes", Cambridge University Press, 1986, page 425. Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.hamming(51) >>> plt.plot(window) >>> plt.title("Hamming window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the Hamming window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") gH�z�G�?r_ r* s r% r r s � �X �1�d�C� (� (�(r' c �\ � t | � � rt j | � � S t | |� � \ } }t j d| � � }| dz dz }t j |t j d||z |z dz z � � z � � t j |� � z }t ||� � S )a� Return a Kaiser window. The Kaiser window is a taper formed by using a Bessel function. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. beta : float Shape parameter, determines trade-off between main-lobe width and side lobe level. As beta gets large, the window narrows. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). Notes ----- The Kaiser window is defined as .. math:: w(n) = I_0\left( \beta \sqrt{1-\frac{4n^2}{(M-1)^2}} \right)/I_0(\beta) with .. math:: \quad -\frac{M-1}{2} \leq n \leq \frac{M-1}{2}, where :math:`I_0` is the modified zeroth-order Bessel function. The Kaiser was named for Jim Kaiser, who discovered a simple approximation to the DPSS window based on Bessel functions. The Kaiser window is a very good approximation to the Digital Prolate Spheroidal Sequence, or Slepian window, which is the transform which maximizes the energy in the main lobe of the window relative to total energy. The Kaiser can approximate other windows by varying the beta parameter. (Some literature uses alpha = beta/pi.) [4]_ ==== ======================= beta Window shape ==== ======================= 0 Rectangular 5 Similar to a Hamming 6 Similar to a Hann 8.6 Similar to a Blackman ==== ======================= A beta value of 14 is probably a good starting point. Note that as beta gets large, the window narrows, and so the number of samples needs to be large enough to sample the increasingly narrow spike, otherwise NaNs will be returned. Most references to the Kaiser window come from the signal processing literature, where it is used as one of many windowing functions for smoothing values. It is also known as an apodization (which means "removing the foot", i.e. smoothing discontinuities at the beginning and end of the sampled signal) or tapering function. References ---------- .. [1] J. F. Kaiser, "Digital Filters" - Ch 7 in "Systems analysis by digital computer", Editors: F.F. Kuo and J.F. Kaiser, p 218-285. John Wiley and Sons, New York, (1966). .. [2] E.R. Kanasewich, "Time Sequence Analysis in Geophysics", The University of Alberta Press, 1975, pp. 177-178. .. [3] Wikipedia, "Window function", https://en.wikipedia.org/wiki/Window_function .. [4] F. J. Harris, "On the use of windows for harmonic analysis with the discrete Fourier transform," Proceedings of the IEEE, vol. 66, no. 1, pp. 51-83, Jan. 1978. :doi:`10.1109/PROC.1978.10837`. Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.kaiser(51, beta=14) >>> plt.plot(window) >>> plt.title(r"Kaiser window ($\beta$=14)") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title(r"Frequency response of the Kaiser window ($\beta$=14)") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") r r! rK ) r& r3 r4 r, rF r �i0�sqrtr1 )r$ �betar+ r< rI rf r/ s r% r r [ s� � �V �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� � �!�Q���A� ��U�c�M�E� ��D�2�7�1��U��e�(;��'C�#C�D�D�D� E� E� ��D� � � �A� �Q� � $� $�$r' rb c �d � |st d� � �| dk rt j g � � S | dz rt d� � �t | dz dz |� � }t j |� � }t j |dd� |d z � � }t j ||ddd� fd�� � }|S ) a Return a Kaiser-Bessel derived window. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. Note that this window is only defined for an even number of points. beta : float Kaiser window shape parameter. sym : bool, optional This parameter only exists to comply with the interface offered by the other window functions and to be callable by `get_window`. When True (default), generates a symmetric window, for use in filter design. Returns ------- w : ndarray The window, normalized to fulfil the Princen-Bradley condition. See Also -------- kaiser Notes ----- It is designed to be suitable for use with the modified discrete cosine transform (MDCT) and is mainly used in audio signal processing and audio coding. .. versionadded:: 1.9.0 References ---------- .. [1] Bosi, Marina, and Richard E. Goldberg. Introduction to Digital Audio Coding and Standards. Dordrecht: Kluwer, 2003. .. [2] Wikipedia, "Kaiser window", https://en.wikipedia.org/wiki/Kaiser_window Examples -------- Plot the Kaiser-Bessel derived window based on the wikipedia reference [2]_: >>> import numpy as np >>> from scipy import signal >>> import matplotlib.pyplot as plt >>> fig, ax = plt.subplots() >>> N = 50 >>> for alpha in [0.64, 2.55, 7.64, 31.83]: ... ax.plot(signal.windows.kaiser_bessel_derived(2*N, np.pi*alpha), ... label=f"{alpha=}") >>> ax.grid(True) >>> ax.set_title("Kaiser-Bessel derived window") >>> ax.set_ylabel("Amplitude") >>> ax.set_xlabel("Sample") >>> ax.set_xticks([0, N, 2*N-1]) >>> ax.set_xticklabels(["0", "N", "2N+1"]) # doctest: +SKIP >>> ax.set_yticks([0.0, 0.2, 0.4, 0.6, 0.707, 0.8, 1.0]) >>> fig.legend(loc="center") >>> fig.tight_layout() >>> fig.show() zCKaiser-Bessel Derived windows are only defined for symmetric shapesr! rC zHKaiser-Bessel Derived windows are only defined for even number of pointsNr. r ��axis)r# r3 �arrayr �cumsumrs re )r$ rt r+ � kaiser_window�csum� half_windowr/ s r% r r � s� � �D � �� � � � � �Q����x��|�|�� �Q�� �� � � � � �1��6�A�:�t�,�,�M� �9�]� #� #�D��'�$�s��s�)�d�2�h�.�/�/�K� �� �[���2��%6�7�a�@�@�@�A� �Hr' c � � t | � � rt j | � � S t | |� � \ } }t j d| � � | dz dz z }d|z |z }t j |dz |z � � }t ||� � S )a^ Return a Gaussian window. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. std : float The standard deviation, sigma. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). Notes ----- The Gaussian window is defined as .. math:: w(n) = e^{ -\frac{1}{2}\left(\frac{n}{\sigma}\right)^2 } Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.gaussian(51, std=7) >>> plt.plot(window) >>> plt.title(r"Gaussian window ($\sigma$=7)") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title(r"Frequency response of the Gaussian window ($\sigma$=7)") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") r rD rK rC )r& r3 r4 r, rF �expr1 )r$ �stdr+ r< rI �sig2r/ s r% r r ( s� � �j �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� � �!�Q���1�s�7�c�/�)�A� �s�7�S�=�D� ���Q��w��~� � �A� �Q� � $� $�$r' c �. � t | � � rt j | � � S t | |� � \ } }t j d| � � | dz dz z }t j dt j ||z � � d|z z z � � }t ||� � S )a� Return a window with a generalized Gaussian shape. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. p : float Shape parameter. p = 1 is identical to `gaussian`, p = 0.5 is the same shape as the Laplace distribution. sig : float The standard deviation, sigma. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). Notes ----- The generalized Gaussian window is defined as .. math:: w(n) = e^{ -\frac{1}{2}\left|\frac{n}{\sigma}\right|^{2p} } the half-power point is at .. math:: (2 \log(2))^{1/(2 p)} \sigma Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.general_gaussian(51, p=1.5, sig=7) >>> plt.plot(window) >>> plt.title(r"Generalized Gaussian window (p=1.5, $\sigma$=7)") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title(r"Freq. resp. of the gen. Gaussian " ... r"window (p=1.5, $\sigma$=7)") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") r rD rK g �rC )r& r3 r4 r, rF r~ rO r1 )r$ �p�sigr+ r< rI r/ s r% r r h s� � �z �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� � �!�Q���1�s�7�c�/�)�A� ��t�b�f�Q��W�o�o�!�a�%�0�0�1�1�A� �Q� � $� $�$r' c �� � t j |� � dk rt j d� � t | � � rt j | � � S t | |� � \ } }| dz }t j d|z t j dt j |� � dz z � � z � � }t j d| � dz }|t j t j |z | z � � z }t j |j � � }t j |t j ||dk � � z � � ||dk < d| dz z dz t j |t j ||d k � � z � � z ||d k < t j |t j |t j |� � dk � � z � � |t j |� � dk < | dz r[t j t! j |� � � � } | dz dz } | d | � } t j | | dz dd � | f� � } n�|t j d t j z | z t j d| � z � � z }t j t! j |� � � � } | dz dz } t j | | dz dd � | d| � f� � } | t) | � � z } t+ | |� � S ) a� Return a Dolph-Chebyshev window. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. at : float Attenuation (in dB). sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value always normalized to 1 Notes ----- This window optimizes for the narrowest main lobe width for a given order `M` and sidelobe equiripple attenuation `at`, using Chebyshev polynomials. It was originally developed by Dolph to optimize the directionality of radio antenna arrays. Unlike most windows, the Dolph-Chebyshev is defined in terms of its frequency response: .. math:: W(k) = \frac {\cos\{M \cos^{-1}[\beta \cos(\frac{\pi k}{M})]\}} {\cosh[M \cosh^{-1}(\beta)]} where .. math:: \beta = \cosh \left [\frac{1}{M} \cosh^{-1}(10^\frac{A}{20}) \right ] and 0 <= abs(k) <= M-1. A is the attenuation in decibels (`at`). The time domain window is then generated using the IFFT, so power-of-two `M` are the fastest to generate, and prime number `M` are the slowest. The equiripple condition in the frequency domain creates impulses in the time domain, which appear at the ends of the window. References ---------- .. [1] C. Dolph, "A current distribution for broadside arrays which optimizes the relationship between beam width and side-lobe level", Proceedings of the IEEE, Vol. 34, Issue 6 .. [2] Peter Lynch, "The Dolph-Chebyshev Window: A Simple Optimal Filter", American Meteorological Society (April 1997) http://mathsci.ucd.ie/~plynch/Publications/Dolph.pdf .. [3] F. J. Harris, "On the use of windows for harmonic analysis with the discrete Fourier transforms", Proceedings of the IEEE, Vol. 66, No. 1, January 1978 Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.chebwin(51, at=100) >>> plt.plot(window) >>> plt.title("Dolph-Chebyshev window (100 dB)") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the Dolph-Chebyshev window (100 dB)") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") �- a This window is not suitable for spectral analysis for attenuation values lower than about 45dB because the equivalent noise bandwidth of a Chebyshev window does not grow monotonically with increasing sidelobe attenuation when the attenuation is smaller than about 45 dB.rD � g 4@r r! rC r. Ny �?)r3 rO �warnings�warnr& r4 r, �cosh�arccoshrG r: r6 r7 rd �arccos�real�sp_fftr re r~ �maxr1 ) r$ �atr+ r< �orderrt r> �xr� r/ rI s r% r r � s� � �l �v�b�z�z�B���� � %� &� &� &� �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� ��G�E� �7�3��;���B�2�6�"�:�:��3C�,D�!E�!E�E� F� F�D� ��a��c� �S��A� �r�v�b�e�a�i�!�m�$�$�$�A� ������A��w�u�r�z�!�A��E�(� 3� 3�3�4�4�A�a�!�e�H��a�!�e��q� �B�G�E�B�J��!�b�&� �z�4J�4J�,J�$K�$K�K�A�a�"�f�I���u�r�y��2�6�!�9�9��>�1B�'C�'C� C�D�D�A�b�f�Q�i�i�1�n�� �1�u� 4� �G�F�J�q�M�M� "� "�� ��U�q�L�� �b�q�b�E�� �N�A�a�!�e�A�b�j�M�1�-� .� .��� ���s�R�U�{�Q����q��s��3�4�4� 4�� �G�F�J�q�M�M� "� "�� ��F�Q�J�� �N�A�a�!�e�A�b�j�M�1�Q�q�S�6�2� 3� 3�� �C��F�F� �A� �Q� � $� $�$r' c � � t | � � rt j | � � S t | |� � \ } }t j t j | z t j d| � � dz z � � }t ||� � S )a� Return a window with a simple cosine shape. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). Notes ----- .. versionadded:: 0.13.0 Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.cosine(51) >>> plt.plot(window) >>> plt.title("Cosine window") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the cosine window") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") >>> plt.show() r rL )r& r3 r4 r, rU r6 rF r1 rA s r% r r / sk � �f �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� ��r�u�q�y�B�I�a��O�O�b� 0�1�2�2�A� �Q� � $� $�$r' rD c �L � |r|�t d� � �t | � � rt j | � � S t | |� � \ } }|�| dz dz }t j d| � � }t j t j ||z � � |z � � }t ||� � S )a� Return an exponential (or Poisson) window. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. center : float, optional Parameter defining the center location of the window function. The default value if not given is ``center = (M-1) / 2``. This parameter must take its default value for symmetric windows. tau : float, optional Parameter defining the decay. For ``center = 0`` use ``tau = -(M-1) / ln(x)`` if ``x`` is the fraction of the window remaining at the end. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). Notes ----- The Exponential window is defined as .. math:: w(n) = e^{-|n-center| / \tau} References ---------- .. [1] S. Gade and H. Herlufsen, "Windows to FFT analysis (Part I)", Technical Review 3, Bruel & Kjaer, 1987. Examples -------- Plot the symmetric window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> M = 51 >>> tau = 3.0 >>> window = signal.windows.exponential(M, tau=tau) >>> plt.plot(window) >>> plt.title("Exponential Window (tau=3.0)") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -35, 0]) >>> plt.title("Frequency response of the Exponential window (tau=3.0)") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") This function can also generate non-symmetric windows: >>> tau2 = -(M-1) / np.log(0.01) >>> window2 = signal.windows.exponential(M, 0, tau2, False) >>> plt.figure() >>> plt.plot(window2) >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") Nz"If sym==True, center must be None.r! rC r ) r# r& r3 r4 r, rF r~ rO r1 )r$ �center�taur+ r< rI r/ s r% r r k s� � �T � ?�v�!��=�>�>�>��1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� �~��A�#���� � �!�Q���A� ����q��x� � � �3�&�'�'�A� �Q� � $� $�$r' � � c � � ��� t � � � rt j � � � S t � |� � \ � }d|dz z }t j |� � t j z }|dz |dz |dz dz z z }t j d|� � �t j |dz � � �t j �� � } d| ddd�< d| ddd�< ��z } t �� � D ]�\ } } | | t j d| | |z |dz �dz dz z z z � � z } dt j d| | | d| � z z � � z t j d| | | | dz d� z z � � z }| |z �| < ���� �fd�} |t j � � � � � }|rd |� dz dz � � z }||z }t ||� � S ) av Return a Taylor window. The Taylor window taper function approximates the Dolph-Chebyshev window's constant sidelobe level for a parameterized number of near-in sidelobes, but then allows a taper beyond [2]_. The SAR (synthetic aperature radar) community commonly uses Taylor weighting for image formation processing because it provides strong, selectable sidelobe suppression with minimum broadening of the mainlobe [1]_. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. nbar : int, optional Number of nearly constant level sidelobes adjacent to the mainlobe. sll : float, optional Desired suppression of sidelobe level in decibels (dB) relative to the DC gain of the mainlobe. This should be a positive number. norm : bool, optional When True (default), divides the window by the largest (middle) value for odd-length windows or the value that would occur between the two repeated middle values for even-length windows such that all values are less than or equal to 1. When False the DC gain will remain at 1 (0 dB) and the sidelobes will be `sll` dB down. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- out : array The window. When `norm` is True (default), the maximum value is normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). See Also -------- chebwin, kaiser, bartlett, blackman, hamming, hann References ---------- .. [1] W. Carrara, R. Goodman, and R. Majewski, "Spotlight Synthetic Aperture Radar: Signal Processing Algorithms" Pages 512-513, July 1995. .. [2] Armin Doerry, "Catalog of Window Taper Functions for Sidelobe Control", 2017. https://www.researchgate.net/profile/Armin_Doerry/publication/316281181_Catalog_of_Window_Taper_Functions_for_Sidelobe_Control/links/58f92cb2a6fdccb121c9d54d/Catalog-of-Window-Taper-Functions-for-Sidelobe-Control.pdf Examples -------- Plot the window and its frequency response: >>> import numpy as np >>> from scipy import signal >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> window = signal.windows.taylor(51, nbar=20, sll=100, norm=False) >>> plt.plot(window) >>> plt.title("Taylor window (100 dB)") >>> plt.ylabel("Amplitude") >>> plt.xlabel("Sample") >>> plt.figure() >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> plt.plot(freq, response) >>> plt.axis([-0.5, 0.5, -120, 0]) >>> plt.title("Frequency response of the Taylor window (100 dB)") >>> plt.ylabel("Normalized magnitude [dB]") >>> plt.xlabel("Normalized frequency [cycles per sample]") r� � rC rL r! Nr. c �� �� ddt j �t j dt j z �d d �t j f z | �dz z dz z �z � � � � z z S )Nr! rC rK rL )r3 �dotr: r6 �newaxis)rI �Fmr$ �mas ���r% �Wztaylor.<locals>.W* sh �� ��1�R�V�B��� �b�e�G�B�q�q�q�"�*�}�%� %�q��2��v�c�z� 2�1� 4�!6� !6� 7� 7� 7� 7� 7r' rD ) r& r3 r4 r, r� r6 rF �empty� empty_like� enumerate�prodr1 )r$ �nbar�sll�normr+ r< �B�A�s2�signs�m2�mi�m�numer�denomr� r/ �scaler� r� s ` @@r% r r � s� ���� �` �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� �S�2�X��A� � �1� � ��� �A� �q��A�q�D�D�3�J��?�*� +�B� ��1�d� � �B� ��$�q�&� � �B� �M�"� � �E��E�#�#�A�#�J��E�!�$�Q�$�K� �B��B��2� � � � ���A��b� �B�G�A��2��r� �1�a�4�2��8�a�-�3G�(H�$H� I� I�I���B�G�A��2��r�#�2�#�w�� .�/�/�/�"�'�!�b��f�R��1����Y�>N�:N�2O�2O�O���� ��2���7� 7� 7� 7� 7� 7� 7� ��"�)�A�,�,���A� � ��a�a��Q��!� �n�n�$�� �U� �� �Q� � $� $�$r' Fc � � t | � � rt j | � � S |�|�dnd}d}||vrt d|�d|��� � �|�d}d}nd }t j |� � }d |cxk r| k sn t d � � �|| d z k rt d � � �|d k rt d� � �t | |� � \ } }t |� � | z } t j | � � } | dz d| z z d z dz t j dt j z | z � � z } | dd� | | dd� z z d z } t j | | d| |z | dz f�� � \ } }| ddd� } |dd�ddd�f j }|ddd� � d�� � d k }t |� � D ]\ }}|r|d|z xx dz cc< �t! dd| z � � }t |ddd� � � D ]4\ }} | | | z |k d d k r|d|z dz xx dz cc< �5|rVt# |� � }d| z t j d| z | z � � z }d| z |d < t j ||� � }|r|d }|dk r�||� � � z }| dz d k r�|dk r | dz t | dz |z � � z }n�t) j |d � � }dd| z z t j d| dz dz � � z }|dd�xx dt j dt j z |z � � z z cc< | |j � � � z }||z }|r|dd�dd�f }|r|d }|r||fn|S )a� Compute the Discrete Prolate Spheroidal Sequences (DPSS). DPSS (or Slepian sequences) are often used in multitaper power spectral density estimation (see [1]_). The first window in the sequence can be used to maximize the energy concentration in the main lobe, and is also called the Slepian window. Parameters ---------- M : int Window length. NW : float Standardized half bandwidth corresponding to ``2*NW = BW/f0 = BW*M*dt`` where ``dt`` is taken as 1. Kmax : int | None, optional Number of DPSS windows to return (orders ``0`` through ``Kmax-1``). If None (default), return only a single window of shape ``(M,)`` instead of an array of windows of shape ``(Kmax, M)``. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. norm : {2, 'approximate', 'subsample'} | None, optional If 'approximate' or 'subsample', then the windows are normalized by the maximum, and a correction scale-factor for even-length windows is applied either using ``M**2/(M**2+NW)`` ("approximate") or a FFT-based subsample shift ("subsample"), see Notes for details. If None, then "approximate" is used when ``Kmax=None`` and 2 otherwise (which uses the l2 norm). return_ratios : bool, optional If True, also return the concentration ratios in addition to the windows. Returns ------- v : ndarray, shape (Kmax, M) or (M,) The DPSS windows. Will be 1D if `Kmax` is None. r : ndarray, shape (Kmax,) or float, optional The concentration ratios for the windows. Only returned if `return_ratios` evaluates to True. Will be 0D if `Kmax` is None. Notes ----- This computation uses the tridiagonal eigenvector formulation given in [2]_. The default normalization for ``Kmax=None``, i.e. window-generation mode, simply using the l-infinity norm would create a window with two unity values, which creates slight normalization differences between even and odd orders. The approximate correction of ``M**2/float(M**2+NW)`` for even sample numbers is used to counteract this effect (see Examples below). For very long signals (e.g., 1e6 elements), it can be useful to compute windows orders of magnitude shorter and use interpolation (e.g., `scipy.interpolate.interp1d`) to obtain tapers of length `M`, but this in general will not preserve orthogonality between the tapers. .. versionadded:: 1.1 References ---------- .. [1] Percival DB, Walden WT. Spectral Analysis for Physical Applications: Multitaper and Conventional Univariate Techniques. Cambridge University Press; 1993. .. [2] Slepian, D. Prolate spheroidal wave functions, Fourier analysis, and uncertainty V: The discrete case. Bell System Technical Journal, Volume 57 (1978), 1371430. .. [3] Kaiser, JF, Schafer RW. On the Use of the I0-Sinh Window for Spectrum Analysis. IEEE Transactions on Acoustics, Speech and Signal Processing. ASSP-28 (1): 105-107; 1980. Examples -------- We can compare the window to `kaiser`, which was invented as an alternative that was easier to calculate [3]_ (example adapted from `here <https://ccrma.stanford.edu/~jos/sasp/Kaiser_DPSS_Windows_Compared.html>`_): >>> import numpy as np >>> import matplotlib.pyplot as plt >>> from scipy.signal import windows, freqz >>> M = 51 >>> fig, axes = plt.subplots(3, 2, figsize=(5, 7)) >>> for ai, alpha in enumerate((1, 3, 5)): ... win_dpss = windows.dpss(M, alpha) ... beta = alpha*np.pi ... win_kaiser = windows.kaiser(M, beta) ... for win, c in ((win_dpss, 'k'), (win_kaiser, 'r')): ... win /= win.sum() ... axes[ai, 0].plot(win, color=c, lw=1.) ... axes[ai, 0].set(xlim=[0, M-1], title=r'$\alpha$ = %s' % alpha, ... ylabel='Amplitude') ... w, h = freqz(win) ... axes[ai, 1].plot(w, 20 * np.log10(np.abs(h)), color=c, lw=1.) ... axes[ai, 1].set(xlim=[0, np.pi], ... title=r'$\beta$ = %0.2f' % beta, ... ylabel='Magnitude (dB)') >>> for ax in axes.ravel(): ... ax.grid(True) >>> axes[2, 1].legend(['DPSS', 'Kaiser']) >>> fig.tight_layout() >>> plt.show() And here are examples of the first four windows, along with their concentration ratios: >>> M = 512 >>> NW = 2.5 >>> win, eigvals = windows.dpss(M, NW, 4, return_ratios=True) >>> fig, ax = plt.subplots(1) >>> ax.plot(win.T, linewidth=1.) >>> ax.set(xlim=[0, M-1], ylim=[-0.1, 0.1], xlabel='Samples', ... title='DPSS, M=%d, NW=%0.1f' % (M, NW)) >>> ax.legend(['win[%d] (%0.4f)' % (ii, ratio) ... for ii, ratio in enumerate(eigvals)]) >>> fig.tight_layout() >>> plt.show() Using a standard :math:`l_{\infty}` norm would produce two unity values for even `M`, but only one unity value for odd `M`. This produces uneven window power that can be counteracted by the approximate correction ``M**2/float(M**2+NW)``, which can be selected by using ``norm='approximate'`` (which is the same as ``norm=None`` when ``Kmax=None``, as is the case here). Alternatively, the slower ``norm='subsample'`` can be used, which uses subsample shifting in the frequency domain (FFT) to compute the correction: >>> Ms = np.arange(1, 41) >>> factors = (50, 20, 10, 5, 2.0001) >>> energy = np.empty((3, len(Ms), len(factors))) >>> for mi, M in enumerate(Ms): ... for fi, factor in enumerate(factors): ... NW = M / float(factor) ... # Corrected using empirical approximation (default) ... win = windows.dpss(M, NW) ... energy[0, mi, fi] = np.sum(win ** 2) / np.sqrt(M) ... # Corrected using subsample shifting ... win = windows.dpss(M, NW, norm='subsample') ... energy[1, mi, fi] = np.sum(win ** 2) / np.sqrt(M) ... # Uncorrected (using l-infinity norm) ... win /= win.max() ... energy[2, mi, fi] = np.sum(win ** 2) / np.sqrt(M) >>> fig, ax = plt.subplots(1) >>> hs = ax.plot(Ms, energy[2], '-o', markersize=4, ... markeredgecolor='none') >>> leg = [hs[-1]] >>> for hi, hh in enumerate(hs): ... h1 = ax.plot(Ms, energy[0, :, hi], '-o', markersize=4, ... color=hh.get_color(), markeredgecolor='none', ... alpha=0.66) ... h2 = ax.plot(Ms, energy[1, :, hi], '-o', markersize=4, ... color=hh.get_color(), markeredgecolor='none', ... alpha=0.33) ... if hi == len(hs) - 1: ... leg.insert(0, h1[0]) ... leg.insert(0, h2[0]) >>> ax.set(xlabel='M (samples)', ylabel=r'Power / $\sqrt{M}$') >>> ax.legend(leg, ['Uncorrected', r'Corrected: $\frac{M^2}{M^2+NW}$', ... 'Corrected (subsample)']) >>> fig.tight_layout() N� approximaterC )rC r� � subsampleznorm must be one of z, got Tr! Fr z+Kmax must be greater than 0 and less than MrK zNW must be less than M/2.zNW must be positive�i)�select� select_ranger. rv gH�����z>rD r� y � �)r& r3 r4 r# �operator�indexr, r@ rF r: r6 r �eigh_tridiagonal�T�sumr� r� � _fftautocorr�sincr� r� �rfftr~ r� )r$ �NW�Kmaxr+ r� � return_ratios� known_norms� singletonr< r� �nidxra �er/ �windows�fix_evenr� �f�thresh�dpss_rxx�r�ratios� correction�s�shifts r% r r 8 s4 � �F �1�~�~� ��w�q�z�z�� �|� $� �}�}�!��1�K� �;� � ��j� '�K�K���/� 0� 0� 0� �|�� ����� � �>�$� � �D� �t�=�=�=�=�q�=�=�=�=��F�G�G�G� �Q�r�T�z�z��4�5�5�5� �Q�w�w��.�/�/�/� �Q��_�_�N�A�{� �b� � �A� �A� �9�Q�<�<�D�( �a�%�!�d�(� �b� �Q�&����B�E� �A� �)>�)>�>�A� �Q�R�R��A��Q�R�R��L�!�B�&�A� �(� �1�S��D��!�a�%�'8�:� :� :�J�A�w� �$�$�B�$��A��a�a�a���2��g� � �G� ���!�� � � �a� �(�(�1�,�H��(�#�#� !� !���1� � !� �A��E�N�N�N�b� �N�N�N�� ��r�A�v� � �F��'�!�$�Q�$�-�(�(� %� %���1� �Q��U�V�^� �Q� �!� #� #� �A��E�A�I� � � �"� $� � � �� � � ��(�(�� ��E�B�G�A��E�D�L�)�)� )���1�u��!�����!�$�$�� � ��A�Y�F� �q�y�y��7�;�;�=�=� �� �q�5�A�:�:��}�$�$� ��T�E�!�Q�$��)�$4�$4� 4� � ��K��� �+�+���b��d�(� �b�i��1�a�4�!�8�&<�&<�<���!�"�"�����R�V�C�"�%�K�%�$7� 8� 8�8�8���� ����� � � -� � �z� !�G�� "��!�!�!�S�b�S�&�/��� ��!�*�� -� :�G�V� � �7�:r' c � � t | � � rt j | � � S t | |� � \ } }d� }| dz dk r6 || dz | � � }t j t j |� � |f }n9 || dz dz | � � }t j t j |� � d|f }t ||� � S )a� Return a Lanczos window also known as a sinc window. Parameters ---------- M : int Number of points in the output window. If zero, an empty array is returned. An exception is thrown when it is negative. sym : bool, optional When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis. Returns ------- w : ndarray The window, with the maximum value normalized to 1 (though the value 1 does not appear if `M` is even and `sym` is True). Notes ----- The Lanczos window is defined as .. math:: w(n) = sinc \left( \frac{2n}{M - 1} - 1 \right) where .. math:: sinc(x) = \frac{\sin(\pi x)}{\pi x} The Lanczos window has reduced Gibbs oscillations and is widely used for filtering climate timeseries with good properties in the physical and spectral domains. .. versionadded:: 1.10 References ---------- .. [1] Lanczos, C., and Teichmann, T. (1957). Applied analysis. Physics Today, 10, 44. .. [2] Duchon C. E. (1979) Lanczos Filtering in One and Two Dimensions. Journal of Applied Meteorology, Vol 18, pp 1016-1022. .. [3] Thomson, R. E. and Emery, W. J. (2014) Data Analysis Methods in Physical Oceanography (Third Edition), Elsevier, pp 593-637. .. [4] Wikipedia, "Window function", http://en.wikipedia.org/wiki/Window_function Examples -------- Plot the window >>> import numpy as np >>> from scipy.signal.windows import lanczos >>> from scipy.fft import fft, fftshift >>> import matplotlib.pyplot as plt >>> fig, ax = plt.subplots(1) >>> window = lanczos(51) >>> ax.plot(window) >>> ax.set_title("Lanczos window") >>> ax.set_ylabel("Amplitude") >>> ax.set_xlabel("Sample") >>> fig.tight_layout() >>> plt.show() and its frequency response: >>> fig, ax = plt.subplots(1) >>> A = fft(window, 2048) / (len(window)/2.0) >>> freq = np.linspace(-0.5, 0.5, len(A)) >>> response = 20 * np.log10(np.abs(fftshift(A / abs(A).max()))) >>> ax.plot(freq, response) >>> ax.set_xlim(-0.5, 0.5) >>> ax.set_ylim(-120, 0) >>> ax.set_title("Frequency response of the lanczos window") >>> ax.set_ylabel("Normalized magnitude [dB]") >>> ax.set_xlabel("Normalized frequency [cycles per sample]") >>> fig.tight_layout() >>> plt.show() c �h � t j dt j | |� � z |dz z dz � � S )NrK r! rD )r3 r� rF )rI r� s r% �_calc_right_side_lanczosz)lanczos.<locals>._calc_right_side_lanczos� s/ � ��w�r�B�I�a��O�O�+�q�1�u�5��;�<�<�<r' rC r r! rD )r& r3 r4 r, rG �flipr1 )r$ r+ r< r� �whr/ s r% r r < s� � �\ �1�~�~� ��w�q�z�z�� �Q��_�_�N�A�{� =� =� =� �1�u��z�z� %� %�a��c�1� -� -�� �E�"�'�"�+�+�r�/� "��� %� %�q��s�A�g�q� 1� 1�� �E�"�'�"�+�+�s�B�&� '�� �Q� � $� $�$r' c �� � | j d }t j d|z dz � � }t j | |d�� � }t j ||� � � z |�� � dd�d|�f }|S )z@Compute the autocorrelation of a real array and crop the result.r. rC r! rv )rI N)rd r� � next_fast_lenr� �irfft�conj)r� �N�use_N�x_fft�cxys r% r� r� � st � � ��� �A� � ��1��Q�� '� '�E� �K��5�r� *� *� *�E� �,�u�u�z�z�|�|�+�u� 5� 5� 5�a�a�a��!��e� <�C� �Jr' )r �brthan�bth)r �bart�brt)r �black�blk)r � blackharr�bkh)r �bman�bmn)r �boxr4 �rect� rectangular)r �cheb)r � halfcosine)r )r �poisson)r �flat�flt)r �gauss�gss)zgeneral cosiner )zgeneral gaussianr z general gauss� general_gauss�ggs)zgeneral hammingr )r �hamm�ham)r �han))r �ksr)zkaiser bessel derived�kbd)r r� )r �nutl�nut)r �parz�par)r � taylorwin)�triangler �tri)r �tukr! c �d � | } t | � � }t }||f}�n # t t f$ r�}d}t | t � � r&| d } t | � � dk r | dd� }ndt | t � � r"| t v rt d| z dz � � |�| } n-t dt t | � � � � z � � |� t | }n"# t $ r}t d� � |�d}~ww xY w|t u r |f|z d z }n|f|z }Y d}~nd}~ww xY w ||d |i�S ) a# Return a window of a given length and type. Parameters ---------- window : string, float, or tuple The type of window to create. See below for more details. Nx : int The number of samples in the window. fftbins : bool, optional If True (default), create a "periodic" window, ready to use with `ifftshift` and be multiplied by the result of an FFT (see also :func:`~scipy.fft.fftfreq`). If False, create a "symmetric" window, for use in filter design. Returns ------- get_window : ndarray Returns a window of length `Nx` and type `window` Notes ----- Window types: - `~scipy.signal.windows.boxcar` - `~scipy.signal.windows.triang` - `~scipy.signal.windows.blackman` - `~scipy.signal.windows.hamming` - `~scipy.signal.windows.hann` - `~scipy.signal.windows.bartlett` - `~scipy.signal.windows.flattop` - `~scipy.signal.windows.parzen` - `~scipy.signal.windows.bohman` - `~scipy.signal.windows.blackmanharris` - `~scipy.signal.windows.nuttall` - `~scipy.signal.windows.barthann` - `~scipy.signal.windows.cosine` - `~scipy.signal.windows.exponential` - `~scipy.signal.windows.tukey` - `~scipy.signal.windows.taylor` - `~scipy.signal.windows.lanczos` - `~scipy.signal.windows.kaiser` (needs beta) - `~scipy.signal.windows.kaiser_bessel_derived` (needs beta) - `~scipy.signal.windows.gaussian` (needs standard deviation) - `~scipy.signal.windows.general_cosine` (needs weighting coefficients) - `~scipy.signal.windows.general_gaussian` (needs power, width) - `~scipy.signal.windows.general_hamming` (needs window coefficient) - `~scipy.signal.windows.dpss` (needs normalized half-bandwidth) - `~scipy.signal.windows.chebwin` (needs attenuation) If the window requires no parameters, then `window` can be a string. If the window requires parameters, then `window` must be a tuple with the first argument the string name of the window, and the next arguments the needed parameters. If `window` is a floating point number, it is interpreted as the beta parameter of the `~scipy.signal.windows.kaiser` window. Each of the window types listed above is also the name of a function that can be called directly to create a window of that type. Examples -------- >>> from scipy import signal >>> signal.get_window('triang', 7) array([ 0.125, 0.375, 0.625, 0.875, 0.875, 0.625, 0.375]) >>> signal.get_window(('kaiser', 4.0), 9) array([ 0.08848053, 0.29425961, 0.56437221, 0.82160913, 0.97885093, 0.97885093, 0.82160913, 0.56437221, 0.29425961]) >>> signal.get_window(('exponential', None, 1.), 9) array([ 0.011109 , 0.03019738, 0.082085 , 0.22313016, 0.60653066, 0.60653066, 0.22313016, 0.082085 , 0.03019738]) >>> signal.get_window(4.0, 9) array([ 0.08848053, 0.29425961, 0.56437221, 0.82160913, 0.97885093, 0.97885093, 0.82160913, 0.56437221, 0.29425961]) r) r r! 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