# Multiply Rows of Matrix by Vector in R (Example)

This article explains how to **do a matrix multiplication with a vector** in the R programming language.

The tutorial will contain these content blocks:

Here’s the step-by-step process:

## Creating Exemplifying Data

Let’s first construct some example data.

my_mat <- matrix(1:12, nrow = 3) # Example matrix my_mat # Print matrix # [,1] [,2] [,3] [,4] # [1,] 1 4 7 10 # [2,] 2 5 8 11 # [3,] 3 6 9 12 |

my_mat <- matrix(1:12, nrow = 3) # Example matrix my_mat # Print matrix # [,1] [,2] [,3] [,4] # [1,] 1 4 7 10 # [2,] 2 5 8 11 # [3,] 3 6 9 12

As you can see based on the previous output of the RStudio console, the example data is a matrix with three rows and four columns.

Let’s also create an example vector (or array):

my_vec <- 1:4 # Example vector my_vec # Print vector # 1 2 3 4 |

my_vec <- 1:4 # Example vector my_vec # Print vector # 1 2 3 4

Our example vector contains of four numeric values ranging from 1 to 4.

## Example: Multiply Matrix by Vector Using sweep Function

The following R programming syntax shows how to use the sweep function to multiply every row of our matrix with our example vector.

sweep(my_mat, MARGIN = 2, my_vec, `*`) # Apply sweep # [,1] [,2] [,3] [,4] # [1,] 1 8 21 40 # [2,] 2 10 24 44 # [3,] 3 12 27 48 |

sweep(my_mat, MARGIN = 2, my_vec, `*`) # Apply sweep # [,1] [,2] [,3] [,4] # [1,] 1 8 21 40 # [2,] 2 10 24 44 # [3,] 3 12 27 48

Have a look at the previous output: We multiplied the lines of our matrix with our vector.

## Video & Further Resources

Would you like to know more about matrix multiplication in R? Then you might watch the following video of my YouTube channel. In the video, I explain the R programming code of this tutorial.

*The YouTube video will be added soon.*

In addition, you may want to have a look at some of the related articles on this homepage:

Summary: In this tutorial you learned how to **multiply matrices and arrays** in the R programming language. If you have additional questions, tell me about it in the comments section.

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