## Matrix in R:

In this tutorial we will learn about matrix in R. All columns in a matrix must have the same mode(numeric, character, etc.) and the same length. The general format of matrix in R is

mymatrix <- **matrix(***vector*, **nrow=***r*, **ncol=***c*, **byrow=***FALSE*)

**byrow=TRUE** indicates that the matrix should be filled by rows. **byrow=FALSE** indicates that the matrix should be filled by columns (the default).

mymatrix <- matrix(c(1,2,3,5,6,7,9,10,12), nrow=3, ncol=3, byrow=FALSE) mymatrix

**output:**

[,1] [,2] [,3]

[1,] 1 5 9

[2,] 2 6 10

[3,] 3 7 12

## Accessing Elements of a Matrix in R:

Elements of a matrix can be accessed by using the row and column index of the element.

# Access the element at 3rd column and 1st row. print(mymatrix[1,3]) # Access the element at 2nd column and 3rd row. print(mymatrix [3,2]) # Access only the 2nd row. print(mymatrix [2,]) # Access only the 3rd column. print(mymatrix [,3])

When we execute the above code, it produces the following result −

[1] 9

[1] 7

[1] 2 6 10

[1] 9 10 12

#### Matrix Computations in R (Matrix addition, Matrix subtraction, Matrix multiplication, Matrix division):

Various mathematical operations are performed on the matrices using the R operators. The result of the operation is also a matrix.

Prerequisite is both the matrices has to be of same dimension

matrix1 <- matrix(c(1, 3, 5, 7), nrow = 2) matrix2 <- matrix(c(2, 4, 6, 8), nrow = 2) # Add the matrices. Mat.Add <- matrix1 matrix2 # Subtract the matrices Mat.Sub <- matrix1 - matrix2 # Multiply the matrices. Mat.Multi <- matrix1 * matrix2 # Divide the matrices Mat.Div <- matrix1 / matrix2

When we execute the above code, it produces the following result

#### Result of Matrix Addition in R:

[,1] [,2]

[1,] 3 11

[2,] 7 15

#### Result of Matrix Subtraction in R

[,1] [,2]

[1,] -1 -1

[2,] -1 -1

#### Result of Matrix Multiplication in R

[,1] [,2]

[1,] 2 30

[2,] 12 56

#### Result of Matrix Division in R

[,1] [,2]

[1,] 0.50 0.8333333

[2,] 0.75 0.8750000