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Python numpy.argmax()用法及代码示例


numpy.argmax(array,axis = None,out = None):返回特定轴上数组max元素的索引。
参数:

array:Input array to work on 
axis :[int, optional]Along a specified axis like 0 or 1
out  :[array optional]Provides a feature to insert output to the out
          array and it should be of appropriate shape and dtype

返回:

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

代码1:


# Python Program illustrating 
# working of argmax() 
  
import numpy as geek  
  
# Working on 2D array 
array = geek.arange(12).reshape(3, 4) 
print("INPUT ARRAY:\n", array) 
  
# No axis mentioned, so works on entire array 
print("\nMax element:", geek.argmax(array)) 
  
# returning Indices of the max element 
# as per the indices 
print("\nIndices of Max element:", geek.argmax(array, axis=0)) 
print("\nIndices of Max element:", geek.argmax(array, axis=1))

输出:

INPUT ARRAY:
 [[ 0  1  2  3]
 [ 4  5  6  7]
 [ 8  9 10 11]]

Max element: 11

Indices of Max element: [2 2 2 2]

Indices of Max element: [3 3 3]

代码2:

# Python Program illustarting 
# working of argmax() 
  
import numpy as geek  
  
# Working on 2D array 
array =  geek.random.randint(16, size=(4, 4)) 
print("INPUT ARRAY:\n", array) 
  
# No axis mentioned, so works on entire array 
print("\nMax element:", geek.argmax(array)) 
  
# returning Indices of the max element 
# as per the indices 
  
'''    
   [[ 0  3  8 13] 
    [12 11  2 11] 
    [ 5 13  8  3] 
    [12 15  3  4]] 
      ^  ^  ^  ^ 
     12 15  8  13  - element 
     1  3   0  0   - indices 
'''
print("\nIndices of Max element:", geek.argmax(array, axis = 0)) 
  
  
'''    
                            ELEMENT   INDEX 
   ->[[ 0  3  8 13]           13        3 
    ->[12 11  2 11]           12        0 
    ->[ 5 13  8  3]           13        1 
    ->[12 15  3  4]]          15        1 
        
'''
print("\nIndices of Max element:", geek.argmax(array, axis = 1))

输出:

INPUT ARRAY:
 [[ 0  3  8 13]
  [12 11  2 11]
  [ 5 13  8  3]
  [12 15  3  4]]

Max element: 15

Indices of Max element: [1 3 0 0]

Indices of Max element: [3 0 1 1]

代码3:

# Python Program illustarting 
# working of argmax() 
  
import numpy as geek  
  
# Working on 2D array 
array =  geek.arange(10).reshape(2, 5) 
print("array:\n", array) 
  
array[0][1] = 6
print("\narray:\n", array) 
       
# Returns max element 
print("\narray:", geek.argmax(array)) 
  
# First occurrence of an max element is given 
print("\nMAX ELEMENT INDICES:", geek.argmax(array, axis = 0))

输出:

array:
 [[0 1 2 3 4]
 [5 6 7 8 9]]

array:
 [[0 6 2 3 4]
 [5 6 7 8 9]]

array: 9

MAX ELEMENT INDICES: [1 0 1 1 1]

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



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