What is the numpy.eye() Method

Numpy.eye() method “returns a 2D array with  1’s as the diagonal and  0’s elsewhere.” The diagonal can be main, upper, or lower depending on the optional parameter k. A positive k is for the upper diagonal, a negative k is for the lower, and a  0 k (default) is for the main diagonal.

Syntax

numpy.eye(N, M=None, k=0, dtype=<class 'float'>, order='C')

Parameters

  1. N: It represents several rows in a 2D array.
  2. M: It represents the number of columns. It is an optional argument; by default, it equals the value N i.e., several rows.
  3. k: This argument is used for representing the Diagonal. It is entirely optional.

By default, it is equal to 0. A positive value (k>0) refers to an upper diagonal, and a negative value(k<0) to a lower diagonal.

  1. dtype: It denotes the data type of the returned array. It is entirely optional, and by default, it is a float.
  2. order: The order parameter can be either C_contiguous or F_contiguous.

Return Value

The numpy.eye() method returns a 2D array of shape, N x M, i.e., a matrix where all elements are equal to zero, except for the kth diagonal, whose values are equal to one.

Example 1: How to Use np.eye() Method

import numpy as np

# 2x2 matrix with 1's on main diagonal
obj1 = np.eye(2, dtype=float)
print("Matrix : \n", obj1)

# matrix with Row=2 Column=3 and diagonal=1
obj2 = np.eye(2, 3, k=1)
print("\nMatrix : \n", obj2)

# matrix with Row=3 Column=3 and diagonal=-1
obj2 = np.eye(3, 3, k=1)
print("\nMatrix : \n", obj2)

Output

Matrix :
 [[1. 0.]
 [0. 1.]]

Matrix :
 [[0. 1. 0.]
 [0. 0. 1.]]

Matrix :
 [[0. 1. 0.]
 [0. 0. 1.]
 [0. 0. 0.]]

Example 2: Identity Matrix using Numpy.eye() function

import numpy as np
 
b = np.eye(2, dtype = float)
print("Matrix b : \n", b)

arr = np.eye(4, 5, k = -1)
print("\nMatrix arr : \n", arr)

Output

Matrix b :
 [[1. 0.]
 [0. 1.]]

Matrix arr :
 [[0. 0. 0. 0. 0.]
  [1. 0. 0. 0. 0.]
  [0. 1. 0. 0. 0.]
  [0. 0. 1. 0. 0.]]

That’s it.

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