Question

我有这个函数返回一个numpy数组，其中包含分别代表x和y坐标的两个向量，我想把它们变成（x; y）对。 / p>

例如：

import numpy as np

def rotate(coords, angle, center=(0, 0,)):
    rotated = np.array([np.cos(np.radians(angle)) * (coords[:,0] - center[0]) - np.sin(np.radians(angle)) * (coords[:,1] - center[1]) + center[0],
                np.sin(np.radians(angle)) * (coords[:,0] - center[0]) + np.cos(np.radians(angle)) * (coords[:,1] - center[1]) + center[1]])
    return rotated

xy = np.array([[1,2],[3,4],[5,6],[6,7]])
a = rotate(xy,20)
print a

这给了我：

[[ 0.25565233  1.45099729  2.64634224  3.24401472]
 [ 2.22140538  4.78483091  7.34825644  8.62996921]]

但是，我实际上想要这个输出：

[[0.25565233, 2.22140538] 
 [1.45099729, 4.78483091]
 [2.64634224, 7.34825644]
 [3.24401472, 8.62996921]]

Answer 1

只需转置。您可以使用numpy.transpose，也可以使用重载运算符.T：

xy = np.array([[1,2],[3,4],[5,6],[6,7]]);
a = rotate(xy,20).T # <--- Modification here

这样做会给出：

>>> print a
[[ 0.25565233  2.22140538]
 [ 1.45099729  4.78483091]
 [ 2.64634224  7.34825644]
 [ 3.24401472  8.62996921]]

如果您想避免转置输出，可以让该功能执行此操作。只需转置rotate函数中返回的内容：

def rotate(coords, angle, center=(0, 0,)):
    rotated = np.array([np.cos(np.radians(angle)) * (coords[:,0] - center[0]) - np.sin(np.radians(angle)) * (coords[:,1] - center[1]) + center[0],
                np.sin(np.radians(angle)) * (coords[:,0] - center[0]) + np.cos(np.radians(angle)) * (coords[:,1] - center[1]) + center[1]])
    return rotated.T #<-- Modification here

因此，您可以在不进一步思考的情况下做您以前做过的事情：

xy = np.array([[1,2],[3,4],[5,6],[6,7]]);
a = rotate(xy,20)

......这给了我们：

>>> print a
[[ 0.25565233  2.22140538]
 [ 1.45099729  4.78483091]
 [ 2.64634224  7.34825644]
 [ 3.24401472  8.62996921]]

Answer 2

你想要transpose它 -

In [3]: n = np.array([[ 0.25565233,  1.45099729,  2.64634224 , 3.24401472],
   ...:  [ 2.22140538 , 4.78483091 , 7.34825644 , 8.62996921]])

In [4]: n
Out[4]:
array([[ 0.25565233,  1.45099729,  2.64634224,  3.24401472],
       [ 2.22140538,  4.78483091,  7.34825644,  8.62996921]])

In [6]: n.T
Out[6]:
array([[ 0.25565233,  2.22140538],
       [ 1.45099729,  4.78483091],
       [ 2.64634224,  7.34825644],
       [ 3.24401472,  8.62996921]])

在你的情况下 -

def rotate(coords, angle, center=(0, 0,)):
        rotated = np.array([np.cos(np.radians(angle)) * (coords[:,0] - center[0]) - np.sin(np.radians(angle)) * (coords[:,1] - center[1]) + center[0],
                    np.sin(np.radians(angle)) * (coords[:,0] - center[0]) + np.cos(np.radians(angle)) * (coords[:,1] - center[1]) + center[1]])
        return rotated


xy = np.array([[1,2],[3,4],[5,6],[6,7]])

a = rotate(xy,20)

print a.T
>> [[ 0.25565233  2.22140538]
 [ 1.45099729  4.78483091]
 [ 2.64634224  7.34825644]
 [ 3.24401472  8.62996921]]

numpy - 创建2D矩阵的问题

2 个答案: