Create a matrix from a list of vectors using R

In R, vectors can be integer, double, character, logical, complex and raw types. A vector is created using the c() function:

a <- c(val1, val2, ...

Creating a List of Vectors

A list of vectors in R is an array of more than one vector kept in a list structure. Creating a list of vectors is done in the following way:

a <- list()  # Create an empty list 'a'
i <- 1       # Initialize i to 1
j <- 4      # Initialize j to 4

# Loop to create 5 vectors and store them in the list
for (k in 1:5) {
  a[[k]] <- c(i:j) 
  i <- i + 1       
  j <- j + 1     
}
print("The list of vectors is: ")
print(a)

[1] "The list of vectors is: "
[[1]]
[1] 1 2 3 4

[[2]]
[1] 2 3 4 5

[[3]]
[1] 3 4 5 6

[[4]]
[1] 4 5 6 7

[[5]]
[1] 5 6 7 8

Matrix from List of Vectors

Matrices in R can be formed from a list of vectors with the help of functions such as do.call() and matrix().

Using do.call() Function

do.call() helps you execute a function (such as rbind()) on a list of arguments. Here's how to use it to form a matrix:

do.call(rbind, a)

Output:

[,1] [,2] [,3] [,4]
[1,] 1 2 3 4
[2,] 2 3 4 5
[3,] 3 4 5 6
[4,] 4 5 6 7
[5,] 5 6 7 8

we call the do.call() function and pass the arguments as rbind and a.

Using matrix() Function

The matrix() function is used to transform a list of vectors into a matrix. To accomplish this, we first transform the list into a single vector with unlist(), then form the matrix:

Syntax:

matrix(data, nrow, ncol, byrow, dimnames)

Where,

• data: is the input vector which represents the elements in the matrix
• nrow: specifies the number of rows to be created
• ncol: specifies the number of columns to be created
• byrow: specifies logical value. If TRUE, matrix will be filled by row. Default value is FALSE.
• dimnames: specifies the names of rows and columns

ug<-list()
i<-1
j<-5

# Create list of vectors
for (k in 1:6){
  ug[[k]]<-c(i:j)
  i<-i+1
  j<-j+1
} 
# Convert list to a matrix
matrix(unlist(ug), byrow=TRUE, nrow=length(ug) )

     [,1] [,2] [,3] [,4] [,5]
[1,]    1    2    3    4    5
[2,]    2    3    4    5    6
[3,]    3    4    5    6    7
[4,]    4    5    6    7    8
[5,]    5    6    7    8    9
[6,]    6    7    8 ...

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Article Tags :

• R Language
• R Matrix-Programs
• AI-ML-DS With R