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Python numpy.isnan()用法及代码示例


关于:
numpy.isnan(array [,out]):逐个元素测试是否为NaN并以布尔数组形式返回结果。
参数:

array:[array_like]Input array or object whose elements, we need to test for infinity
out  :[ndarray, optional]Output array placed with result.
      Its type is preserved and it must be of the right shape to hold the output.

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

输出:

Is NaN: False 

Is NaN: False 

Is NaN: True 

Is NaN: False 

Is NaN: False 

Checking for NaN: [0 0 0]

代码2:

# Python Program illustrating 
# numpy.isnan() method 
    
import numpy as geek  
   
# Returns True/False value for each element  
b = geek.arange(20).reshape(5, 4) 
                 
print("\n",b) 
print("\nIs NaN(Not a Number):\n", geek.isnan(b)) 
  
  
b = [[1j],  
     [geek.nan]] 
print("\nIs NaN(Not a Number):\n", geek.isnan(b))

输出:

 [[ 0  1  2  3]
 [ 4  5  6  7]
 [ 8  9 10 11]
 [12 13 14 15]
 [16 17 18 19]]

Is NaN(Not a Number):
 [[False False False False]
 [False False False False]
 [False False False False]
 [False False False False]
 [False False False False]]

Is NaN(Not a Number):
 [[False]
 [ True]]

参考文献:
https://docs.scipy.org/doc/numpy-dev/reference/generated/numpy.isnan.html



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