Python numpy.argmax()

Python numpy.argmax()函数返回数组中最大元素在特定axis上的下标。

语法 :

numpy.argmax(array, axis = None, out = None)

参数 :

array : 输入数组来工作。
axis : [int, optional]沿着一个指定的轴，如0或1。
out : [array optional]提供了一个插入输出到out数组的功能，它应该是适当的形状和dtype。

返回 :

与array.shape相同形状的数组，去掉了沿轴线的维度，是数组的索引。

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 illustrating
# 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 illustrating
# 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]