NumPy argmin()

argmin() Syntax

The syntax of argmin() is:

numpy.argmin(array, axis = None, out = None, keepdims = <no value>)

argmin() Arguments

The argmin() method takes four arguments:

• array - input array
• axis (optional) - axis along which index is returned (int)
• out (optional) - array to store the output
• keepdims (optional) - whether to preserve the input array's dimension (bool)

argmin() Return Value

The argmin() method returns the index of the smallest element.

Example 1: argmin() With String

The argmin() method with an array of string or char returns the index of the smallest element based on ASCII value.

Output

0

Example 2: argmin() With 2D Array

The axis argument defines how to handle the index of the smallest element in a 2D array.

• If axis = None, the array is flattened and the index of the flattened array is returned.
• If axis = 0, the index of the smallest element in each column is returned.
• If axis = 1, the index of the smallest element in each row is returned.

Output

Index of the smallest element in the flattened array:  0
Index of the smallest element in each column (axis 0):  [0 1 1]
Index of the smallest element in each row (axis 1):  [0 1]

Example 3: argmin() With 'out' Array

In our previous examples, the argmin() function generated a new array as output.

However, we can use an existing array to store the output using the out argument.

Output

[0 1 2]

Example 4: argmin() With keepdims

When keepdims = True, the dimensions of the resulting array matches the dimension of an input array.

Output

Shape of original array:  (2, 3)

 Without keepdims: 
[0 1]
Shape of array:  (2,)

 With keepdims: 
 [[0]
 [1]]
Shape of array:  (2, 1)

Without keepdims, the result is simply a one-dimensional array of indices.

With keepdims, the resulting array has the same number of dimensions as the input array.

Similarly, with axis = 1 and keepdims = True, the resulting array has the same number of rows as the input array, but its columns have a single element i.e. the index of the smallest element in that column.