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Matrix of sliding window ngrams without any copying via numpy striding tricks
from numpy.lib.stride_tricks import as_strided
def ngrams_via_striding(array, order):
itemsize = array.itemsize
assert array.strides == (itemsize,)
return as_strided(array, (max(array.size + 1 - order, 0), order), (itemsize, itemsize))
In [71]: a = numpy.arange(10)
In [72]: ngrams_via_striding(a, 4)
Out[72]:
array([[0, 1, 2, 3],
[1, 2, 3, 4],
[2, 3, 4, 5],
[3, 4, 5, 6],
[4, 5, 6, 7],
[5, 6, 7, 8],
[6, 7, 8, 9]])
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