In this tutorial, you will learn all about **matrices in R**. We will see what a matrix is, how to create matrices, adding data to matrices, and modifying matrices.

Matrix is a two-dimensional data structure in R, which has rows and columns as two dimensions. A row is used to represent the horizontal representation of the data, and a column is used to represent the vertical representation of the data.

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Table of Contents

## How to Create Matrix in R

We can create a matrix in R using the matrix() function.

**Syntax:**

matrix(data,nrow,ncol)

where,

- data is the input vector that holds elements
- nrow represents the number of rows that should be present in a matrix.
- ncol represents the number of columns that should be present in a matrix.

**Example 1:** We will create a matrix with 6 integer elements with 2 rows using nrow parameter.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=2) #display matrix print(my_matrix)

**Output**:

[,1] [,2] [,3] [1,] 34 78 45 [2,] 56 655 43

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**Example 2:** We will create a matrix with 6 integer elements with 2 columns using ncol parameter.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),ncol=2) #display matrix print(my_matrix)

**Output**:

[,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43

**Example 3:** We will create a matrix with 6 integer elements with 3 rows and 2 columns using nrow and ncol parameters.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=3,ncol=2) #display matrix print(my_matrix)

**Output:**

[,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43

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**Example 4:** We will create a matrix with 6 string elements with 3 rows and 2 columns using nrow and ncol parameters.

#create a matrix with 6 string elements my_matrix=matrix(c("php","c","cpp","html","java","mysql database"),nrow=3,ncol=2) #display matrix print(my_matrix)

**Output**:

[,1] [,2] [1,] "php" "html" [2,] "c" "java" [3,] "cpp" "mysql database"

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## How to access elements in an R matrix

We can access elements in a matrix using the index of elements; indexing starts with 1. By row and column index, we can access a particular element.

**Syntax:**

my_matrix[row_index,column_index]

where,

- my_matrix is the input matrix
- row_index represents row index value
- column_index represents column index value

**Example: **We will create an integer matrix with 3 rows and 2 columns and particular access elements in this example.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=3,ncol=2) #display matrix print(my_matrix) #access element present in first row and second column print(my_matrix[1,2]) #access element present in third row and second column print(my_matrix[3,2]) #access element present in first row and first column print(my_matrix[1,1]) #access element present in third row and first column print(my_matrix[3,1])

**Output:**

[,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43 [1] 655 [1] 43 [1] 34 [1] 78

We can access all the elements present in a row by specifying only the row index.

**Syntax:**

my_matrix[row_index,]

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**Example: **We will create an integer matrix with 3 rows and 2 columns and particular access elements from rows in this example.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=3,ncol=2) #display matrix print(my_matrix) #access elements present in first row print(my_matrix[1,]) #access elemenst present in third row print(my_matrix[3,])

**Output:**

[,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43 [1] 34 655 [1] 78 43

We can access all the elements present in a particular column by specifying only the column index.

**Syntax:**

my_matrix[,column_index]

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**Example: **We will create an integer matrix with 3 rows and 2 columns and access particular elements from the columns in this example.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=3,ncol=2) #display matrix print(my_matrix) #access elements present in first column print(my_matrix[,1]) #access elemenst present in second column print(my_matrix[,2])

**Output**:

[,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43 [1] 34 56 78 [1] 655 45 43

If we want to access more than one row at a time, we can specify row indices in a vector.

**Syntax**:

my_matrix[c(row_indices),]

Where c() represents a vector that takes row indices.

**Example:**

In this example, we will access elements in a matrix from more than one row at a time.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=3,ncol=2) #display matrix print(my_matrix) #access elements present in first, second and third rows print(my_matrix[c(1,2,3),]) #access elements present in first and third rows print(my_matrix[c(1,3),])

**Output:**

[,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43 [,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43 [,1] [,2] [1,] 34 655 [2,] 78 43

If we want to access more than one column at a time, we can specify column indices in a vector.

**Syntax:**

my_matrix[,c(column_indices)]

Where c() represents a vector that takes column indices.

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**Example: **In this example, we will access elements in a matrix from more than one column at a time.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=3,ncol=2) #display matrix print(my_matrix) #access elements present in first, second columns print(my_matrix[,c(1,2)])

**Output:**

[,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43 [,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43

## How to add a row in an R matrix

We can add a row to the existing matrix using the rbind() function.

**Syntax:**

rbind(my_matrix, elements)

where,

- my_matrix is the input matrix
- elements represent row elements to be added through a vector.

**Example:**

In this example, we will add a row to the existing matrix.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=3,ncol=2) #display matrix print(my_matrix) #add a row with integer elements my_matrix=rbind(my_matrix, c(90,100)) #display matrix print(my_matrix)

**Output:**

[,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43 [,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43 [4,] 90 100

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## How to add a column in an R matrix

We can add a column to the existing matrix using the cbind() function.

**Syntax:**

cbind(my_matrix, elements)

where,

- my_matrix is the input matrix
- elements represent column elements to be added through a vector.

**Example:**

In this example, we will add a column to the existing matrix.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=3,ncol=2) #display matrix print(my_matrix) #add a column with integer elements my_matrix=cbind(my_matrix, c(90,100,110)) #display matrix print(my_matrix)

**Output:**

[,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43 [,1] [,2] [,3] [1,] 34 655 90 [2,] 56 45 100 [3,] 78 43 110

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## How to remove elements in an R matrix

We can remove elements in a matrix using the index of elements. Indexing starts with 1. By row and column index, we can remove a particular element.

**Syntax:**

my_matrix[-row_index,-column_index]

where,

- my_matrix is the input matrix
- row_index represents row index value
- column_index represents column index value.

**Example 1**: In this example, we will remove the first row.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=3,ncol=2) #display matrix print(my_matrix) #remove first row my_matrix=my_matrix[-1,] #display matrix print(my_matrix)

**Output:**

[,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43 [,1] [,2] [1,] 56 45 [2,] 78 43

**Example 2**: In this example, we will remove the first column.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=3,ncol=2) #display matrix print(my_matrix) #remove first column my_matrix=my_matrix[,-1] #display matrix print(my_matrix)

**Output**:

[,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43 [1] 655 45 43

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## How to check if elements exist in an R matrix

We can check if an element exists in a matrix or not by using the %in% operator. If an element exists, it will return TRUE, else FALSE.

**Syntax:**

element %in% my_matrix

**Example:**

In this example, we will check whether the given element exists in a matrix or not.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=3,ncol=2) #display matrix print(my_matrix) #check 655 present in matrix or not print(655 %in% my_matrix) #check 34 present in matrix or not print(34 %in% my_matrix) #check 567 present in matrix or not print(567 %in% my_matrix)

**Output:**

[,1] [,2] [1,] 34 655 [2,] 56 45 [3,] 78 43 [1] TRUE [1] TRUE [1] FALSE

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## How to get R matrix dimensions

We will get the number of rows and columns in a matrix using the dim() function.

**Syntax:**

dim(my_matrix)

**Example:**

Get the dimensions of the matrix.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=3,ncol=2) #display the dimensions of the matrix print(dim(my_matrix))

**Output:**

[1] 3 2

If we want to get the total number of elements in a matrix, we will use the length() function.

**Syntax**:

length(my_matrix)

**Example:**

Get the total number of elements from a matrix.

#create a matrix with 6 values my_matrix=matrix(c(34,56,78,655,45,43),nrow=3,ncol=2) #display the length of the matrix print(length(my_matrix))

**Output:**

[1] 6

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### Wrapping Up

Here you explore everything about matrices in R. From this tutorial, you learned how to create a matrix with rows and columns, add rows and columns to a matrix, delete rows and columns from a matrix and get the total number of elements in a matrix we also discussed how to check whether the element exists in a matrix or not.