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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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.
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