Question

我有两个列表列表。

x = [[992,982,...],...,[241,251,...]]
y = [[1184,1178,...],...,[274,294,...]]

我希望获得x和y之间的角度作为列表列表

angles =[[0.87,0.874,...],...,[0.5,0.52,... ]]

我的代码如下：

angles = []
for i in range(1,10):
    for item1 in x[i]:
        for item2 in y[i]:
            angles.append(np.arctan2(item2, item1))

这给了我作为列表的角度。

angles = [0.87,0.874,...]

我希望将角度作为列表列表。任何帮助将不胜感激。

Answer 1

也可能最容易为数组使用numpy。

x_arr = np.array(x)
y_arr = np.array(y)
angles_arr = np.arctan2(x_arr, y_arr)
angles = angles_arr.tolist()

Answer 2

In [53]: x = [[992,982],[241,251]]
    ...: y = [[1184,1178],[274,294]]
    ...:

您的列表迭代：

In [56]: angles = []
In [57]: for i in range(2):
    ...:     for item1 in x[i]:
    ...:         for item2 in y[i]:
    ...:             angles.append(math.atan2(item2,item1))
    ...:             
In [58]: angles
Out[58]: 
[0.8734055369251891,
 0.870903457075653,
 0.8783886606617618,
 0.8758910778163088,
 0.8493883488678455,
 0.8841414043445257,
 0.8291796919394373,
 0.8641341374390786]

在一个级别上分解该列表迭代：

In [59]: angles = []
In [60]: for i in range(2):
    ...:     alist = []
    ...:     for item1 in x[i]:
    ...:         for item2 in y[i]:
    ...:             alist.append(math.atan2(item2,item1))
    ...:     angles.append(alist)
    ...:             
In [61]: angles
Out[61]: 
[[0.8734055369251891,
  0.870903457075653,
  0.8783886606617618,
  0.8758910778163088],
 [0.8493883488678455,
  0.8841414043445257,
  0.8291796919394373,
  0.8641341374390786]]

我可以添加另一个级别列表追加来获得2组2组2。

数组元素配对仅产生4个值：

In [62]: X = np.array(x); Y = np.array(y)
In [63]: np.arctan2(Y,X)
Out[63]: 
array([[0.87340554, 0.87589108],
       [0.84938835, 0.86413414]])

我可以使用广播来获得8个值

In [65]: np.arctan2(Y[:,None,:],X[:,:,None])
Out[65]: 
array([[[0.87340554, 0.87090346],
        [0.87838866, 0.87589108]],

       [[0.84938835, 0.8841414 ],
        [0.82917969, 0.86413414]]])

请注意，这是一个3d数组（2,2,2）。

相反，我只能从循环中得到4个值：

In [66]: angles = []
In [67]: for i in range(2):
    ...:     alist = []
    ...:     for item1, item2 in zip(x[i],y[i]):
    ...:         alist.append(math.atan2(item2,item1))
    ...:     angles.append(alist)
    ...:     
    ...:             
In [68]: angles
Out[68]: 
[[0.8734055369251891, 0.8758910778163088],
 [0.8493883488678455, 0.8641341374390786]]

使用标量math.atan2时的速度比np.arctan2快。

或者以列表理解形式：

In [72]: [[[math.atan2(item2,item1)] for item1, item2 in zip(x[i],y[i])] for i in range(2)]
Out[72]: 
[[[0.8734055369251891], [0.8758910778163088]],
 [[0.8493883488678455], [0.8641341374390786]]]

对列表中的列表中的值进行计算

2 个答案: