Unlock the Power of NumPy’s Eye Method

What is the Eye Method?

The eye method is a powerful tool in NumPy that allows you to create a 2D array with 1s on the diagonal and 0s elsewhere. This method is essential for linear algebra operations and can be used in a variety of applications.

Understanding the Syntax

The syntax of the eye method is straightforward:

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

Let’s break down each argument:

• N: The number of rows in the output array.
• M: The number of columns in the output array. If not specified, it defaults to N.
• k: The diagonal in question. A value of 0 represents the main diagonal, while positive values represent diagonals above the main diagonal and negative values represent diagonals below.
• dtype: The data type of the resultant array.
• order: The memory layout of the array, which can be either ‘C’ (C-style, row-wise) or ‘F’ (Fortran-style, column-wise).

Creating Arrays with Eye

The eye method returns an array with shape NxM, where all elements are 0 except for the kth diagonal, which is filled with 1s. Here are some examples:

Example 1: Square Array

Create a 3×3 square array using the eye method:

import numpy as np

array = np.eye(3)
print(array)

[[1. 0. 0.]
 [0. 1. 0.]
 [0. 0. 1.]]

Example 2: Non-Square Array

Create a 3×4 non-square array by passing both N and M arguments:

import numpy as np

array = np.eye(3, 4)
print(array)

[[1. 0. 0. 0.]
 [0. 1. 0. 0.]
 [0. 0. 1. 0.]]

Example 3: Customizing the Data Type

Use the dtype argument to specify the data type of the created array:

import numpy as np

array = np.eye(3, dtype='U1')
print(array)

[['1' '' '']
 ['' '1' '']
 ['' '' '1']]

Note that when the array is converted to a string array, the 0s are replaced by empty strings.

Controlling the Memory Layout

The order argument allows you to specify the memory layout of the array. You can choose between ‘C’ (C-style, row-wise) and ‘F’ (Fortran-style, column-wise) layouts.