Split array into equal sized windows

Question

I am trying to split an numpy.array of length 40 into smaller, equal-sized numpy.arrays, in which the number of the smaller arrays is given by the user. It is allowed to have some overlap between the smaller arrays, as situations can occur where the full length is only divisible by the splits given some form of overlap of the smaller arrays.

If I had an array np.array([range(40)]) And I had to split it into 37 sub arrays, the list of subarrays should be like this:

[1, 2, 3], [3, 4, 5], [5, 6, 7], ... [38, 39, 40]

I tried using numpy.split but this only works when the length is divisible by the size, and numpy.array_split generates uneven sizes.

Example using numpy.split

>> import numpy as np
>>> a = np.random.randint(6,size=(40))
>>> b = np.split(a,37)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/site-packages/numpy/lib/shape_base.py", line 508, in split
    'array split does not result in an equal division')
ValueError: array split does not result in an equal division

And with numpy.array_split

>>> a = np.random.randint(5,size=(40))
>>> b = np.array_split(a,37)
>>> print len(b)
37
>>> print b[0].shape
(2,)
>>> print b[3].shape
(1,)
>>> print b[5].shape
(1,)
>>> print b[6].shape
(1,)
>>> print b[30].shape
(1,)
>>> 

numpy.array_split don't equally divide them.

Any solution?

Answer 1

What you're describing is called a (sliding) window, not a split.

See this answer: https://stackoverflow.com/a/15722507/7802200

What you want is to use the window_stack function developed there with a width of len(a) - n_splits + 1.