Python numpy.isnan()用法及代碼示例

關於：
numpy.isnan(array [，out])：逐個元素測試是否為NaN並以布爾數組形式返回結果。
參數：

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.

代碼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)) 
  

輸出：

Is NaN: False 

Is NaN: False 

Is NaN: True 

Is NaN: False 

Is NaN: False 

Checking for NaN: [0 0 0]

代碼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))

輸出：

 [[ 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]]

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