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# Matrix product of a 1D (first argument) and a 2D array (second argument) in Numpy

To find the matrix product of a 2D and a 1D array, use the **numpy.matmul()** method in Python Numpy. If the first argument is 1-D, it is promoted to a matrix by prepending a 1 to its dimensions. After matrix multiplication the prepended 1 is removed.

Returns the matrix product of the inputs. This is a scalar only when both x1, x2 are 1-d vectors. The out is a location into which the result is stored. If provided, it must have a shape that matches the signature (n,k),(k,m)->(n,m). If not provided or None, a freshly-allocated array is returned.

## Steps

At first, import the required library −

import numpy as np

Create a 1D and a 2D array −

arr1 = np.array([25, 35]) arr2 = np.array([[5, 7], [10, 15]])

Display the arrays −

print("Array 1 (Two Dimensional)...\n", arr1) print("\nArray 2 (One Dimensional)...\n", arr2)

Get the type of the arrays −

print("\nOur Array 1 type...\n", arr1.dtype) print("\nOur Array 2 type...\n", arr2.dtype)

Get the dimensions of the Arrays −

print("\nOur Array 1 Dimensions...\n",arr1.ndim) print("\nOur Array 2 Dimensions...\n",arr2.ndim)

Get the shape of the Arrays −

print("\nOur Array 1 Shape...\n",arr1.shape) print("\nOur Array 2 Shape...\n",arr2.shape)

To find the matrix product of a 2D and a 1D array, use the numpy.matmul() method in Python Numpy. If the first argument is 1-D, it is promoted to a matrix by prepending a 1 to its dimensions. After matrix multiplication the prepended 1 is removed −

print("\nResult (matrix product)...\n",np.matmul(arr1, arr2))

## Example

import numpy as np # Create a 1D and a 2D array arr1 = np.array([25, 35]) arr2 = np.array([[5, 7], [10, 15]]) # Display the arrays print("Array 1 (Two Dimensional)...\n", arr1) print("\nArray 2 (One Dimensional)...\n", arr2) # Get the type of the arrays print("\nOur Array 1 type...\n", arr1.dtype) print("\nOur Array 2 type...\n", arr2.dtype) # Get the dimensions of the Arrays print("\nOur Array 1 Dimensions...\n",arr1.ndim) print("\nOur Array 2 Dimensions...\n",arr2.ndim) # Get the shape of the Arrays print("\nOur Array 1 Shape...\n",arr1.shape) print("\nOur Array 2 Shape...\n",arr2.shape) # To find the matrix product of a 2D and a 1D array, use the numpy.matmul() method in Python Numpy # If the first argument is 1-D, it is promoted to a matrix by prepending a 1 to its dimensions. # After matrix multiplication the prepended 1 is removed. print("\nResult (matrix product)...\n",np.matmul(arr1, arr2))

## Output

Array 1 (Two Dimensional)... [25 35] Array 2 (One Dimensional)... [[ 5 7] [10 15]] Our Array 1 type... int64 Our Array 2 type... int64 Our Array 1 Dimensions... 1 Our Array 2 Dimensions... 2 Our Array 1 Shape... (2,) Our Array 2 Shape... (2, 2) Result (matrix product)... [475 700]

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