# NumPy matrix()

The matrix() method is used to create a matrix from a 2-D array-like object.

### Example

import numpy as np

# create  2-D array
array1 = [[1, 2], [3, 4]]

# use of matrix() to create matrix result = np.matrix(array1)
print(result) ''' Output: [[1 2] [3 4]] '''

## matrix() Syntax

The syntax of matrix() is:

numpy.matrix(data, dtype=None, copy=True)

## matrix() Arguments

The matrix() method takes the following arguments:

• data - input data used to create the matrix
• dtype (optional) - data type of the matrix
• copy (optional) - determines whether a copy of data should be made or not

## matrix() Return Value

The matrix() method returns a matrix object from an array-like object.

## Example 1: Create a Matrix

import numpy as np

# create a list
array1 = [[1, 2, 3],
[4, 5, 6],
[7, 8, 9]]

# use matrix() to create a matrix result = np.matrix(array1, dtype = int)
print(result)

Output

[[1 2 3]
[4 5 6]
[7 8 9]]

If unspecified, the default dtype is float.

## Example 2: Use of copy Argument in matrix()

import numpy as np

# create a 2-D array
array1 = [[1, 2], [3, 4]]

# create matrix with default copy=True
matrix1 = np.matrix(array1)

# modify the original data
array1[0][0] = 5

# create matrix with copy=False
matrix2 = np.matrix(array1, copy=False)

print("Matrix with copy=True:")
print(matrix1)

print("Matrix with copy=False:")
print(matrix2)

Output

Matrix with copy=True:
[[1 2]
[3 4]]
Matrix with copy=False:
[[5 2]
[3 4]]

In the above example, when creating matrices using matrix() with copy=True, a copy of the data is made, resulting in a separate matrix.

With copy=False, the matrix shares the data with the original object. Modifying the original data affects the matrix.