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Deprecate mlab.stride_windows. #21190

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Sep 27, 2021
Merged

Deprecate mlab.stride_windows. #21190

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4 changes: 4 additions & 0 deletions doc/api/next_api_changes/deprecations/ZZZZZ-AL.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
``mlab.stride_windows``
~~~~~~~~~~~~~~~~~~~~~~~
... is deprecated. Use ``np.lib.stride_tricks.sliding_window_view`` instead
(or ``np.lib.stride_tricks.as_strided`` on numpy<1.20).
19 changes: 15 additions & 4 deletions lib/matplotlib/mlab.py
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Expand Up @@ -215,6 +215,7 @@ def detrend_linear(y):
return y - (b*x + a)


@_api.deprecated("3.6")
def stride_windows(x, n, noverlap=None, axis=0):
"""
Get all windows of x with length n as a single array,
Expand Down Expand Up @@ -246,6 +247,18 @@ def stride_windows(x, n, noverlap=None, axis=0):
"""
if noverlap is None:
noverlap = 0
if np.ndim(x) != 1:
raise ValueError('only 1-dimensional arrays can be used')
return _stride_windows(x, n, noverlap, axis)


def _stride_windows(x, n, noverlap=0, axis=0):
# np>=1.20 provides sliding_window_view, and we only ever use axis=0.
if hasattr(np.lib.stride_tricks, "sliding_window_view") and axis == 0:
if noverlap >= n:
raise ValueError('noverlap must be less than n')
return np.lib.stride_tricks.sliding_window_view(
x, n, axis=0)[::n - noverlap].T

if noverlap >= n:
raise ValueError('noverlap must be less than n')
Expand All @@ -254,8 +267,6 @@ def stride_windows(x, n, noverlap=None, axis=0):

x = np.asarray(x)

if x.ndim != 1:
raise ValueError('only 1-dimensional arrays can be used')
if n == 1 and noverlap == 0:
if axis == 0:
return x[np.newaxis]
Expand Down Expand Up @@ -370,15 +381,15 @@ def _spectral_helper(x, y=None, NFFT=None, Fs=None, detrend_func=None,
raise ValueError(
"The window length must match the data's first dimension")

result = stride_windows(x, NFFT, noverlap, axis=0)
result = _stride_windows(x, NFFT, noverlap)
result = detrend(result, detrend_func, axis=0)
result = result * window.reshape((-1, 1))
result = np.fft.fft(result, n=pad_to, axis=0)[:numFreqs, :]
freqs = np.fft.fftfreq(pad_to, 1/Fs)[:numFreqs]

if not same_data:
# if same_data is False, mode must be 'psd'
resultY = stride_windows(y, NFFT, noverlap)
resultY = _stride_windows(y, NFFT, noverlap)
resultY = detrend(resultY, detrend_func, axis=0)
resultY = resultY * window.reshape((-1, 1))
resultY = np.fft.fft(resultY, n=pad_to, axis=0)[:numFreqs, :]
Expand Down
7 changes: 6 additions & 1 deletion lib/matplotlib/tests/test_mlab.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@
import numpy as np
import pytest

import matplotlib.mlab as mlab
from matplotlib import mlab, _api


class TestStride:
Expand All @@ -13,6 +13,11 @@ def get_base(self, x):
y = y.base
return y

@pytest.fixture(autouse=True)
def stride_is_deprecated(self):
with _api.suppress_matplotlib_deprecation_warning():
yield

def calc_window_target(self, x, NFFT, noverlap=0, axis=0):
"""
This is an adaptation of the original window extraction algorithm.
Expand Down