NumPy function argmax

np.argmax is a NumPy function that returns the indices of the maximum values along a specified axis in an array. If the input array is multi-dimensional, you can specify the axis along which the maximum values are computed.

Here’s a simple example:

import numpy as np

arr = np.array([1, 5, 2, 8, 3])

# Get the index of the maximum value in the array
index_of_max_value = np.argmax(arr)

print("Array:", arr)
print("Index of Maximum Value:", index_of_max_value)
print("Maximum Value:", arr[index_of_max_value])

Output:

Array: [1 5 2 8 3]
Index of Maximum Value: 3
Maximum Value: 8

In this example, np.argmax(arr) returns the index (position) of the maximum value in the array arr. The maximum value is 8, and it is at index 3 (0-indexed).

You can also use np.argmax with multi-dimensional arrays and specify the axis along which the maximum values should be computed. For example:

import numpy as np

arr_2d = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])

# Get the indices of the maximum values along each column (axis=0)
indices_of_max_values = np.argmax(arr_2d, axis=0)

print("2D Array:")
print(arr_2d)
print("Indices of Maximum Values along Each Column:", indices_of_max_values)

Output:

2D Array:
[[1 2 3]
 [4 5 6]
 [7 8 9]]
Indices of Maximum Values along Each Column: [2 2 2]

In this 2D array example, np.argmax(arr_2d, axis=0) returns the indices of the maximum values along each column (axis=0). The result is an array [2, 2, 2], indicating that the maximum values in each column are found in the third row.