`scipy.signal._arraytools:odd_ext`

Signature

def odd_ext ( x , n , axis = -1 )

Odd extension at the boundaries of an array

Generate a new ndarray by making an odd extension of x along an axis.

x : ndarray: The array to be extended.
n : int: The number of elements by which to extend x at each end of the axis.
axis : int, optional: The axis along which to extend x. Default is -1.

import numpy as np
from scipy.signal._arraytools import odd_ext
a = np.array([[1, 2, 3, 4, 5], [0, 1, 4, 9, 16]])
odd_ext(a, 2)

✓

Odd extension is a "180 degree rotation" at the endpoints of the original array:

t = np.linspace(0, 1.5, 100)
a = 0.9 * np.sin(2 * np.pi * t**2)
b = odd_ext(a, 40)
import matplotlib.pyplot as plt

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plt.plot(np.arange(-40, 140), b, 'b', lw=1, label='odd extension')
plt.plot(np.arange(100), a, 'r', lw=2, label='original')
plt.legend(loc='best')

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plt.show()

✓