Python。 numwise配列の反復

Question

nwiseの反復を効率的に実行できるnumpy関数はありますか？

# http://seriously.dontusethiscode.com/2013/04/28/nwise.html 
from itertools import tee, islice 
nwise = lambda xs, n=2: zip(*(islice(xs, idx, None) for idx, xs in enumerate(tee(xs, n)))) 

例：要素にnwiseを適用しますか？移動平均を取得するには？

Answer 1

汎用：より良いavgを移動

import numpy as np 
from numpy.lib.stride_tricks import as_strided 

def moving_slice(a, k): 
    a = a.ravel() 
    return as_strided(a, (a.size - k + 1, k), 2 * a.strides) 

：

def moving_avg(a, k): 
    ps = np.cumsum(a) 
    return (ps[k-1:] - np.r_[0, ps[:-k]])/k 

例：

a = np.arange(10) 

moving_avg(a, 4) 
# array([ 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5]) 

ms = moving_slice(a, 4) 
ms 
# 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]]) 

# no data are copied: 
a[4] = 0 
ms 
# array([[0, 1, 2, 3], 
#  [1, 2, 3, 0], 
#  [2, 3, 0, 5], 
#  [3, 0, 5, 6], 
#  [0, 5, 6, 7], 
#  [5, 6, 7, 8], 
#  [6, 7, 8, 9]])