Python中的 numpy.arctan2()

numpy.arctan2()方法计算 arr1/arr2 的元素反正切，正确选择象限。选择象限，使得arctan2(x1, x2)是在原点结束并通过点 (1, 0) 的光线与在原点结束并通过点 (x2) 之间的有符号弧度角, x1)。

Syntax : numpy.arctan2(arr1, arr2, casting = ‘same_kind’, order = ‘K’, dtype = None, ufunc ‘arctan’) 
Parameters : 
arr1 : [array_like] real valued; y-coordinates 
arr2 : [array_like] real valued; x-coordinates. It must match shape of y-coordinates. 
out : [ndarray, array_like [OPTIONAL]] array of same shape as x. 
where : [array_like, optional] True value means to calculate the universal functions(ufunc) at that position, False value means to leave the value in the output alone.
Note : 
2pi Radians = 360 degrees 
The convention is to return the angle z whose real part lies in [-pi/2, pi/2].
Return : Element-wise arc tangent of arr1/arr2. The values are in the closed interval [-pi / 2, pi / 2]. 
 

代码#1：工作

Python3

# Python3 program explaining
# arctan2() function
 
import numpy as np
 
arr1 = [-1, +1, +1, -1]
arr2 = [-1, -1, +1, +1]
 
ans = np.arctan2(arr2, arr1) * 180 / np.pi
 
print ("x-coordinates : ", arr1)
print ("y-coordinates : ", arr2)
 
print ("\narctan2 values : \n", ans)

输出 ：

x-coordinates :  [-1, 1, 1, -1]
y-coordinates :  [-1, -1, 1, 1]

arctan2 values : 
 [-135.  -45.   45.  135.]

代码 #2：工作

Python3

# Python3 program showing
# of arctan2() function
 
import numpy as np
 
a = np.arctan2([0., 0., np.inf], [+0., -0., np.inf])
 
b = np.arctan2([1., -1.], [0., 0.])
 
print ("a : ", a)
 
print ("b : ", b)

输出 ：

a :  [ 0.          3.14159265  0.78539816]
b :  [ 1.57079633 -1.57079633]

参考 ：
https://docs.scipy.org/doc/numpy-1.13.0/reference/generated/numpy.arctan2.html#numpy.arctan2
.