Algebraic Operations on a Matrix in R

Matrix is a rectangular arrangement of numbers in rows and columns. In a matrix, as we know rows are the ones that run horizontally and columns are the ones that run vertically. In R matrices are two-dimensional, homogeneous data structures. These are some examples of matrices.

Basic algebraic operations are any one of the traditional operations of arithmetic, which are addition, subtraction, multiplication, division, raising to an integer power, and taking roots. These operations may be performed on numbers, in which case they are often called arithmetic operations. We can perform many more algebraic operations on a matrix in R. Algebraic operations that can be performed on a matrix in R:

  • Operations on a single matrix
  • Unary operations
  • Binary operations
  • Linear algebraic operations
    • Rank, determinant, transpose, inverse, trace of a matrix
    • Nullity of a matrix
    • Eigenvalues and eigenvectors of matrices
    • Solve a linear matrix equation

Operations on a single matrix

We can use overloaded arithmetic operators to do element-wise operation on a matrix to create a new matrix. In case of +=, -=, *= operators, the existing matrix is modified.

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# R program to demonstrate
# basic operations on a single matrix
  
# Create a 3x3 matrix
a = matrix(
  c(1, 2, 3, 4, 5, 6, 7, 8, 9), 
  nrow = 3,             
  ncol = 3,             
  byrow = TRUE          
)
cat("The 3x3 matrix:\n")
print(a)
  
# add 1 to every element
cat("Adding 1 to every element:\n")
print(a + 1)
  
# subtract 3 from each element
cat("Subtracting 3 from each element:\n")
print(a-3)
  
# multiply each element by 10
cat("Multiplying each element by 10:\n")
print(a * 10)
  
# square each element
cat("Squaring each element:\n")
print(a ^ 2)
  
# modify existing matrix
cat("Doubled each element of original matrix:\n")
print(a * 2)

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Output:



The 3x3 matrix:
     [, 1] [, 2] [, 3]
[1, ]    1    2    3
[2, ]    4    5    6
[3, ]    7    8    9
Adding 1 to every element:
     [, 1] [, 2] [, 3]
[1, ]    2    3    4
[2, ]    5    6    7
[3, ]    8    9   10
Subtracting 3 from each element:
     [, 1] [, 2] [, 3]
[1, ]   -2   -1    0
[2, ]    1    2    3
[3, ]    4    5    6
Multiplying each element by 10:
     [, 1] [, 2] [, 3]
[1, ]   10   20   30
[2, ]   40   50   60
[3, ]   70   80   90
Squaring each element:
     [, 1] [, 2] [, 3]
[1, ]    1    4    9
[2, ]   16   25   36
[3, ]   49   64   81
Doubled each element of original matrix:
     [, 1] [, 2] [, 3]
[1, ]    2    4    6
[2, ]    8   10   12
[3, ]   14   16   18

Unary operations

Many unary operations can be performed on a matrix in R. This includes sum, min, max, etc.

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# R program to demonstrate
# unary operations on a matrix
  
# Create a 3x3 matrix
a = matrix(
  c(1, 2, 3, 4, 5, 6, 7, 8, 9), 
  nrow = 3,             
  ncol = 3,             
  byrow = TRUE          
)
cat("The 3x3 matrix:\n")
print(a)
  
# maximum element in the matrix
cat("Largest element is:\n")
print(max(a))
  
# minimum element in the matrix
cat("Smallest element is:\n")
print(min(a))
  
# sum of element in the matrix
cat("Sum of elements is:\n")
print(sum(a))

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Output:

The 3x3 matrix:
     [, 1] [, 2] [, 3]
[1, ]    1    2    3
[2, ]    4    5    6
[3, ]    7    8    9
Largest element is:
[1] 9
Smallest element is:
[1] 1
Sum of elements is:
[1] 45

Binary operations

These operations apply on a matrix elementwise and a new matrix is created. You can use all basic arithmetic operators like +, -, *, /, etc. In case of +=, -=, = operators, the existing matrix is modified.

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# R program to demonstrate
# binary operations on a matrix
  
# Create a 3x3 matrix
a = matrix(
  c(1, 2, 3, 4, 5, 6, 7, 8, 9), 
  nrow = 3,             
  ncol = 3,             
  byrow = TRUE          
)
cat("The 3x3 matrix:\n")
print(a)
  
# Create another 3x3 matrix
b = matrix(
  c(1, 2, 5, 4, 6, 2, 9, 4, 3), 
  nrow = 3,             
  ncol = 3,             
  byrow = TRUE          
)
cat("The another 3x3 matrix:\n")
print(b)
  
cat("Matrix addition:\n")
print(a + b)
  
cat("Matrix substraction:\n")
print(a-b)
  
cat("Matrix element wise multiplication:\n")
print(a * b)
  
cat("Regular Matrix multiplication:\n")
print(a %*% b)
  
cat("Matrix elementwise division:\n")
print(a / b)

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Output:

The 3x3 matrix:
     [, 1] [, 2] [, 3]
[1, ]    1    2    3
[2, ]    4    5    6
[3, ]    7    8    9
The another 3x3 matrix:
     [, 1] [, 2] [, 3]
[1, ]    1    2    5
[2, ]    4    6    2
[3, ]    9    4    3
Matrix addition:
     [, 1] [, 2] [, 3]
[1, ]    2    4    8
[2, ]    8   11    8
[3, ]   16   12   12
Matrix substraction:
     [, 1] [, 2] [, 3]
[1, ]    0    0   -2
[2, ]    0   -1    4
[3, ]   -2    4    6
Matrix element wise multiplication:
     [, 1] [, 2] [, 3]
[1, ]    1    4   15
[2, ]   16   30   12
[3, ]   63   32   27
Regular Matrix multiplication:
     [, 1] [, 2] [, 3]
[1, ]   36   26   18
[2, ]   78   62   48
[3, ]  120   98   78
Matrix elementwise division:
          [, 1]      [, 2] [, 3]
[1, ] 1.0000000 1.0000000  0.6
[2, ] 1.0000000 0.8333333  3.0
[3, ] 0.7777778 2.0000000  3.0

Linear algebraic operations

One can perform many linear algebraic operations on a given matrix In R. Some of them are as follows:

  • Rank, determinant, transpose, inverse, trace of a matrix:
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    # R program to demonstrate
    # Linear algebraic operations on a matrix
      
    # Importing required library
    library(pracma) # For rank of matrix
    library(psych)  # For trace of matrix
      
    # Create a 3x3 matrix
    A = matrix(
      c(6, 1, 1, 4, -2, 5, 2, 8, 7), 
      nrow = 3,             
      ncol = 3,             
      byrow = TRUE          
    )
    cat("The 3x3 matrix:\n")
    print(A)
      
    # Rank of a matrix
    cat("Rank of A:\n")
    print(Rank(A))
      
    # Trace of matrix A
    cat("Trace of A:\n")
    print(tr(A))
      
    # Determinant of a matrix
    cat("Determinant of A:\n")
    print(det(A))
      
    # Transpose of a matrix
    cat("Transpose of A:\n")
    print(t(A))
      
    # Inverse of matrix A
    cat("Inverse of A:\n")
    print(inv(A))

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    Output:

    The 3x3 matrix:
         [, 1] [, 2] [, 3]
    [1, ]    6    1    1
    [2, ]    4   -2    5
    [3, ]    2    8    7
    Rank of A:
    [1] 3
    Trace of A:
    [1] 11
    Determinant of A:
    [1] -306
    Transpose of A:
         [, 1] [, 2] [, 3]
    [1, ]    6    4    2
    [2, ]    1   -2    8
    [3, ]    1    5    7
    Inverse of A:
                [, 1]         [, 2]        [, 3]
    [1, ]  0.17647059 -0.003267974 -0.02287582
    [2, ]  0.05882353 -0.130718954  0.08496732
    [3, ] -0.11764706  0.150326797  0.05228758
    
  • Nullity of a matrix:
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    # R program to demonstrate
    # nullity of a matrix
      
    # Importing required library
    library(pracma)
      
    # Create a 3x3 matrix
    a = matrix(
      c(1, 2, 3, 4, 5, 6, 7, 8, 9), 
      nrow = 3,             
      ncol = 3,             
      byrow = TRUE          
    )
    cat("The 3x3 matrix:\n")
    print(a)
      
    # No of column
    col = ncol(a)
      
    # Rank of matrix
    rank = Rank(a)
      
    # Calculating nullity
    nullity = col - rank
      
    cat("Nullity of matrix is:\n")
    print(nullity)

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    Output:

    The 3x3 matrix:
         [, 1] [, 2] [, 3]
    [1, ]    1    2    3
    [2, ]    4    5    6
    [3, ]    7    8    9
    Nullity of matrix is:
    [1] 1
    
  • Eigenvalues and eigenvectors of matrices:
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    # R program to illustrate
    # Eigenvalues and eigenvectors of metrics
      
    # Create a 3x3 matrix
    A = matrix(
      c(1, 2, 3, 4, 5, 6, 7, 8, 9), 
      nrow = 3,             
      ncol = 3,             
      byrow = TRUE          
    )
    cat("The 3x3 matrix:\n")
    print(A)
      
    # Calculating Eigenvalues and eigenvectors
    print(eigen(A))

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    Output:

    The 3x3 matrix:
         [, 1] [, 2] [, 3]
    [1, ]    1    2    3
    [2, ]    4    5    6
    [3, ]    7    8    9
    eigen() decomposition
    $values
    [1]  1.611684e+01 -1.116844e+00 -1.303678e-15
    
    $vectors
               [, 1]        [, 2]       [, 3]
    [1, ] -0.2319707 -0.78583024  0.4082483
    [2, ] -0.5253221 -0.08675134 -0.8164966
    [3, ] -0.8186735  0.61232756  0.4082483
    
  • Solve a linear matrix equation:
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    # R program to illustrate
    # Solve a linear matrix equation of metrics
      
    # Importing library for applying pseudoinverse
    library(MASS)
      
    # Create a 2x2 matrix
    A = matrix(
      c(1, 2, 3, 4), 
      nrow = 2,             
      ncol = 2,             
    )
    cat("A = :\n")
    print(A)
      
    # Create another 2x1 matrix
    b = matrix(
      c(7, 10), 
      nrow = 2,             
      ncol = 1,             
    )
    cat("b = :\n")
    print(b)
      
    cat("Solution of linear equations:\n")
    print(solve(A)%*% b)
      
    cat("Solution of linear equations using pseudoinverse:\n")
    print(ginv(A)%*% b)

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    Output:

    A = :
         [, 1] [, 2]
    [1, ]    1    3
    [2, ]    2    4
    b = :
         [, 1]
    [1, ]    7
    [2, ]   10
    Solution of linear equations:
         [, 1]
    [1, ]    1
    [2, ]    2
    Solution of linear equations using pseudoinverse:
         [, 1]
    [1, ]    1
    [2, ]    2
    



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