How to do Matrix Multiplication in R

How to do Matrix Multiplication in R ?

Answer

To perform matrix multiplication in R, you can use the %*% operator. This operator is used to multiply two matrices according to the rules of linear algebra, where the number of columns in the first matrix must equal the number of rows in the second matrix.

✐ Examples

1 Multiplying Two 2x2 Matrices

In this example,

We create the first matrix named matrix1 with values from 1 to 4 arranged in 2 rows and 2 columns using the matrix() function.
We create the second matrix named matrix2 with values from 5 to 8 arranged in 2 rows and 2 columns using the matrix() function.
We use the %*% operator to multiply matrix1 by matrix2. The multiplication is performed according to the rules of linear algebra, where each element of the resulting matrix is the sum of the products of corresponding elements from the rows of the first matrix and the columns of the second matrix.
The resulting matrix is stored in a variable named result_matrix.
Finally, we print the value of result_matrix to standard output to see the result of the matrix multiplication.

R Program

matrix1 <- matrix(1:4, nrow = 2, ncol = 2)
matrix2 <- matrix(5:8, nrow = 2, ncol = 2)
result_matrix <- matrix1 %*% matrix2
print(result_matrix)

Output

     [,1] [,2]
[1,]   19   22
[2,]   43   50

2 Multiplying a 2x3 Matrix by a 3x2 Matrix

In this example,

We create the first matrix named matrix1 with values from 1 to 6 arranged in 2 rows and 3 columns using the matrix() function.
We create the second matrix named matrix2 with values from 7 to 12 arranged in 3 rows and 2 columns using the matrix() function.
We use the %*% operator to multiply matrix1 by matrix2. The multiplication is performed according to the rules of linear algebra, where each element of the resulting matrix is the sum of the products of corresponding elements from the rows of the first matrix and the columns of the second matrix.
The resulting matrix is stored in a variable named result_matrix.
Finally, we print the value of result_matrix to standard output to see the result of the matrix multiplication.

R Program

matrix1 <- matrix(1:6, nrow = 2, ncol = 3)
matrix2 <- matrix(7:12, nrow = 3, ncol = 2)
result_matrix <- matrix1 %*% matrix2
print(result_matrix)

Output

     [,1] [,2]
[1,]   58   64
[2,]  139  154

3 Multiplying Two 3x3 Matrices

In this example,

We create the first matrix named matrix1 with values from 1 to 9 arranged in 3 rows and 3 columns using the matrix() function.
We create the second matrix named matrix2 with values from 10 to 18 arranged in 3 rows and 3 columns using the matrix() function.
We use the %*% operator to multiply matrix1 by matrix2. The multiplication is performed according to the rules of linear algebra, where each element of the resulting matrix is the sum of the products of corresponding elements from the rows of the first matrix and the columns of the second matrix.
The resulting matrix is stored in a variable named result_matrix.
Finally, we print the value of result_matrix to standard output to see the result of the matrix multiplication.

R Program

matrix1 <- matrix(1:9, nrow = 3, ncol = 3)
matrix2 <- matrix(10:18, nrow = 3, ncol = 3)
result_matrix <- matrix1 %*% matrix2
print(result_matrix)

Output

     [,1] [,2] [,3]
[1,]   84   90   96
[2,]  201  216  231
[3,]  318  342  366

Summary

In this tutorial, we learned How to do Matrix Multiplication in R language with well detailed examples.

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How to do Matrix Multiplication in R

How to do Matrix Multiplication in R ?

Answer

✐ Examples

1 Multiplying Two 2x2 Matrices

R Program

Output

2 Multiplying a 2x3 Matrix by a 3x2 Matrix

R Program

Output

3 Multiplying Two 3x3 Matrices

R Program

Output

Summary

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