numpy.nanargmin() in Python

Last Updated : 08 Mar, 2024

The numpy.nanargmin() function returns indices of the min element of the array in a particular axis ignoring NaNs.
The results cannot be trusted if a slice contains only NaNs and Infs.

Syntax:

numpy.nanargmin(array, axis = None)

Parameters :

array : Input array to work on   axis  : [int, optional]Along a specified axis like 0 or 1

Return :

Array of indices into the array with same shape as array.shape.   with the dimension along axis removed.

Code 1 :

Python

   # Python Program illustrating 
# working of nanargmin() 
  
import numpy as geek  
  
# Working on 1D array 
array = [geek.nan, 4, 2, 3, 1] 
print("INPUT ARRAY 1 : \n", array) 
  
array2 = geek.array([[geek.nan, 4], [1, 3]]) 
  
# returning Indices of the min element 
# as per the indices ingnoring NaN 
print("\nIndices of min in array1 : ", 
      geek.nanargmin(array)) 
  
# Working on 2D array 
print("\nINPUT ARRAY 2 : \n", array2) 
print("\nIndices of min in array2 : ", 
      geek.nanargmin(array2)) 
  
print("\nIndices at axis 1 of array2 : ", 
      geek.nanargmin(array2, axis = 1)) 
 
  

Output :

INPUT ARRAY 1 :    [nan, 4, 2, 3, 1]    Indices of min in array1 :  4    INPUT ARRAY 2 :    [[ nan   4.]   [  1.   3.]]    Indices of min in array2 :  2    Indices at axis 1 of array2 :  [1 0]

Code 2 : Comparing working of argmin and nanargmin

Python

   # Python Program illustrating 
# working of nanargmin() 
  
import numpy as geek  
  
# Working on 2D array 
array = ( [[ 8, 13, 5, 0], 
           [ geek.nan, geek.nan, 5, 3], 
           [10, 7, 15, 15], 
           [3, 11, 4, 12]]) 
print("INPUT ARRAY : \n", array) 
  
# returning Indices of the min element 
# as per the indices  
  
'''    
   [[ 8 13  5  0] 
   [ 0  2  5  3] 
   [10  7 15 15] 
   [ 3 11  4 12]] 
     ^  ^  ^  ^ 
     0  2  4  0  - element 
     1  1  3  0  - indices 
'''
  
print("\nIndices of min using argmin : ", 
      geek.argmin(array, axis = 0)) 
print("\nIndices of min using nanargmin :  : ", 
      geek.nanargmin(array, axis = 0)) 
 
  

Output :

INPUT ARRAY :    [[ 8 13  5  0]   [ 0  2  5  3]   [10  7 15 15]   [ 3 11  4 12]]    Indices of min element :  [1 1 3 0]

Note :
These codes won’t run on online IDE’s. So please, run them on your systems to explore the working.

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