Python中的 numpy.isneginf()

numpy.isneginf()函数按元素测试它是否为负无穷大，并将结果作为布尔数组返回。
句法 ：

numpy.isneginf(array, y = None)

参数 ：

array : [array_like]Input array or object whose elements, we need to test for infinity.
y     : [array_like]A boolean array with the same shape and type as x to store the result.

返回 ：

boolean array containing the result. For scalar input, the result is a new boolean with value
True if the input is positive or negative infinity; otherwise the value is False.
For array input, the result is a boolean array with the same shape as the input and the values
are True where the corresponding element of the input is positive or negative infinity; 
elsewhere the values are False.

代码 1：

Python

# Python Program illustrating
# numpy.isneginf() method
  
import numpy as geek
 
print("Negative : ", geek.isneginf(1), "\n")
 
print("Negative : ", geek.isneginf(0), "\n")
 
# not a number
print("Negative : ", geek.isneginf(geek.nan), "\n")
 
#  infinity
print("Negative : ", geek.isneginf(geek.inf), "\n")
 
print("Negative : ", geek.isneginf(geek.NINF), "\n")
 
x = geek.array([-geek.inf, 0., geek.inf])
y = geek.array([2, 2, 2])
print("Checking for negativity : ", geek.isneginf(x, y))

输出 ：

Negative :  False 

Negative :  False 

Negative :  False 

Negative :  False 

Negative :  True 

Checking for negativity :  [1 0 0]

代码 2：

Python

# Python Program illustrating
# numpy.isneginf() method
   
import numpy as geek
  
# Returns True/False value for each element
b = geek.arange(18).reshape(3, 6)
                
print("\n",b)
print("\nIs Negative Infinity : \n", geek.isneginf(b))
 
# geek.inf  : Positive Infinity
# geek.NINF : negative Infinity
b = [[geek.inf],
     [geek.NINF]]
print("\nIs Negative Infinity : \n", geek.isneginf(b))

输出 ：

[[ 0  1  2  3  4  5]
 [ 6  7  8  9 10 11]
 [12 13 14 15 16 17]]

Is Negative Infinity : 
 [[False False False False False False]
 [False False False False False False]
 [False False False False False False]]

Is Negative Infinity : 
 [[False]
 [ True]]