随机排列二维数组的行组 - NumPy

Question

假设我有一个 (50, 5) 数组。有没有一种方法可以根据 rows/sequences 数据点的分组对其进行洗牌，即不是洗牌每一行，而是洗牌 5 行？

谢谢

Answer 1

方法 #1： 这是一种根据组大小重塑为 3D 数组的方法，使用从 np.random.permutation 最后重塑回 2D -

N = 5 # Blocks of N rows
M,n = a.shape[0]//N, a.shape[1]
out = a.reshape(M,-1,n)[np.random.permutation(M)].reshape(-1,n)

样本运行-

In [141]: a
Out[141]: 
array([[89, 26, 12],
       [97, 60, 96],
       [94, 38, 54],
       [41, 63, 29],
       [88, 62, 48],
       [95, 66, 32],
       [28, 58, 80],
       [26, 35, 89],
       [72, 91, 38],
       [26, 70, 93]])

In [142]: N = 2 # Blocks of N rows

In [143]: M,n = a.shape[0]//N, a.shape[1]

In [144]: a.reshape(M,-1,n)[np.random.permutation(M)].reshape(-1,n)
Out[144]: 
array([[94, 38, 54],
       [41, 63, 29],
       [28, 58, 80],
       [26, 35, 89],
       [89, 26, 12],
       [97, 60, 96],
       [72, 91, 38],
       [26, 70, 93],
       [88, 62, 48],
       [95, 66, 32]])

方法 #2 : 也可以简单地使用 np.random.shuffle 进行 in-situ 更改 -

np.random.shuffle(a.reshape(M,-1,n))

样本运行-

In [156]: a
Out[156]: 
array([[15, 12, 14],
       [55, 39, 35],
       [73, 78, 36],
       [54, 52, 32],
       [83, 34, 91],
       [42, 11, 98],
       [27, 65, 47],
       [78, 75, 82],
       [33, 52, 93],
       [87, 51, 80]])

In [157]: N = 2 # Blocks of N rows

In [158]: M,n = a.shape[0]//N, a.shape[1]

In [159]: np.random.shuffle(a.reshape(M,-1,n))

In [160]: a
Out[160]: 
array([[15, 12, 14],
       [55, 39, 35],
       [27, 65, 47],
       [78, 75, 82],
       [73, 78, 36],
       [54, 52, 32],
       [33, 52, 93],
       [87, 51, 80],
       [83, 34, 91],
       [42, 11, 98]])

随机排列二维数组的行组 - NumPy

Shuffle groups of rows of a 2D array - NumPy

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shuffle

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