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bugfix: scaling of windows with negative coefficients #22828

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bugfix: scaling of windows with negative coefficients #22828

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bugfix: scaling of windows with negative coefficients 
For proper scaling of the magnitude a division by the sum
of all window elements is needed.
To be able to handle complex window coefficients an abs()
was introduced in a622508
which falsifies the scaling for windows with negative
coefficients. Most prominently the flattop window.

A proper type check is introduced to handle both cases
correctly.
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LucasIsOnline
LucasIsOnline committed Apr 11, 2022
commit 7b2d4aff01358f9eeca6ac541dcb4b39f15bd706
6 changes: 5 additions & 1 deletion lib/matplotlib/mlab.py
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Expand Up @@ -395,7 +395,11 @@ def _spectral_helper(x, y=None, NFFT=None, Fs=None, detrend_func=None,
elif mode == 'psd':
result = np.conj(result) * result
elif mode == 'magnitude':
result = np.abs(result) / np.abs(window).sum()
result = np.abs(result)
if np.iscomplexobj(window):

@jklymak jklymak Jan 31, 2023

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I don't think you need to check for complex windows here.

result /= np.abs(window).sum()
else:
result /= np.asarray(window).sum()
elif mode == 'angle' or mode == 'phase':
# we unwrap the phase later to handle the onesided vs. twosided case
result = np.angle(result)
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