我有一个形状为(x, y)的二维数组,我想将其转换为形状为(x, y, 1)的三维数组。有没有一种好的Pythonic方法来实现这个转换?
我有一个形状为(x, y)的二维数组,我想将其转换为形状为(x, y, 1)的三维数组。有没有一种好的Pythonic方法来实现这个转换?
除了其他答案外,您还可以使用numpy.newaxis
的切片:
>>> from numpy import zeros, newaxis
>>> a = zeros((6, 8))
>>> a.shape
(6, 8)
>>> b = a[:, :, newaxis]
>>> b.shape
(6, 8, 1)
甚至可以使用以下代码(适用于任意维数):
>>> b = a[..., newaxis]
>>> b.shape
(6, 8, 1)
numpy.reshape(array, array.shape + (1,))
A
,您可以简单地将其分配给形状属性: A.shape = A.shape + (1,)
,甚至是 A.shape += 1,
。 - Mark Dickinsonreshape
函数可以吗? - seralouknp.reshape
内使用order='F'
时,所得到的结果是期望的。如果没有指定order='F'
,那么在我的情况下输出就是错误的。 - seraloukimport numpy as np
# create a 2D array
a = np.array([[1,2,3], [4,5,6], [1,2,3], [4,5,6],[1,2,3], [4,5,6],[1,2,3], [4,5,6]])
print(a.shape)
# shape of a = (8,3)
b = np.reshape(a, (8, 3, -1))
# changing the shape, -1 means any number which is suitable
print(b.shape)
# size of b = (8,3,1)
import numpy as np
a= np.eye(3)
print a.shape
b = a.reshape(3,3,1)
print b.shape
Args:
x: 2darray, (n_time, n_in)
agg_num: int, number of frames to concatenate.
hop: int, number of hop frames.
Returns:
3darray, (n_blocks, agg_num, n_in)
def d_2d_to_3d(x, agg_num, hop):
# Pad to at least one block.
len_x, n_in = x.shape
if (len_x < agg_num): #not in get_matrix_data
x = np.concatenate((x, np.zeros((agg_num - len_x, n_in))))
# main 2d to 3d.
len_x = len(x)
i1 = 0
x3d = []
while (i1 + agg_num <= len_x):
x3d.append(x[i1 : i1 + agg_num])
i1 += hop
return np.array(x3d)
如果您只想将第三个轴(x,y)添加到(x,y,1),Numpy允许您使用dstack
命令轻松完成此操作。
import numpy as np
a = np.eye(3) # your matrix here
b = np.dstack(a).T
.T
),以便将其转换为你想要的 (x,y,1) 格式。import numpy as np
# create a 2-D ndarray
a = np.array([[2,3,4], [5,6,7]])
print(a.ndim)
>> 2
print(a.shape)
>> (2, 3)
# add 3rd dimension
第一种选择:重新塑形
b = np.reshape(a, a.shape + (1,))
print(b.ndim)
>> 3
print(b.shape)
>> (2, 3, 1)
2nd option: expand_dims
c = np.expand_dims(a, axis=2)
print(c.ndim)
>> 3
print(c.shape)
>> (2, 3, 1)
用一些数学方法来简单实现
首先,你需要知道数组元素的数量,比如说100个。
然后将100分为3步,例如:
25 * 2 * 2 = 100
或者:4 * 5 * 5 = 100
import numpy as np
D = np.arange(100)
# change to 3d by division of 100 for 3 steps 100 = 25 * 2 * 2
D3 = D.reshape(2,2,25) # 25*2*2 = 100
another_3D = D.reshape(4,5,5)
print(another_3D.ndim)
给4D:
D4 = D.reshape(2,2,5,5)
print(D4.ndim)
a2 = np.array([[1, 2, 3.3],
[4, 5, 6.5]])
然后您可以使用以下代码将此数组更改为形状为 (2,3,3)
的 3 维数组:
a2_new = np.reshape(a2, a2.shape + (1,)) a2_new
你的输出将是:
array([[[1. ],
[2. ],
[3.3]],
[[4. ],
[5. ],
[6.5]]])
或者 你可以尝试:
a2.reshape(2, 3, 1)
这将把你的二维数组转换为三维的shape(2, 3, 1)
。
numpy.newaxis
就是None
。newaxis
只是为了可读性而存在。等价于这样做b = a[..., None]
(省略号允许其适用于多维数组,而不仅仅是二维数组)。 - Joe Kingtonnewaxis
是None
只是一种实现细节(因此可能会在将来更改),但看起来它明确地记录下来了。 - Mark Dickinsona
转换为b
,其中b.shape = (6,8,3)
? - Gathide(6,8,1)
并利用NumPy的广播能力即可。但是,如果您确实需要形状为(6,8,3)
,请查看np.tile
和np.broadcast_to
。 - Mark Dickinsonnp.broadcast_to
来实现此操作,如下所示:b = np.broadcast_to(a[..., np.newaxis], (6, 8, 3))
。 - wingr