How to create an array in R

The array is the fundamental data structure in R used to store multiple elements of the same data type. In this article, we will explore two different approaches to creating an array in R Programming Language.

Creating an array in R

Below are the approaches for creating an array in R.

• Using array() function
• Using matrix() function

Creating an array Using array() function

array(data, dim = NULL, dimnames = NULL)

• data: The data elements to be arranged into the array.
• dim: An optional parameter specifying the dimensions of the array.
• dimnames: An optional parameter providing names for each dimension of the array.

The below example shows how we can create an array using array() function.

# Creating a 1-dimensional array
arr1d <- array(1:5)

# Creating a multi-dimensional array
arrMulti <- array(1:12, dim = c(3, 4))

# Print the arrays with proper spacing
cat("1-Dimensional Array:\n")
print(arr1d)

cat("\nMulti-Dimensional Array:\n")
print(arrMulti)

Output:

1-Dimensional Array:
[1] 1 2 3 4 5

Multi-Dimensional Array:
     [,1] [,2] [,3] [,4]
[1,]    1    4    7   10
[2,]    2    5    8   11
[3,]    3    6    9   12

In this approach, we are using the array() function in R to create arrays. We start by creating a 1 dimensional array using the array(1:5) syntax, which contains elements from 1 to 5. Then, we create a multidimensional array using the array(1:12, dim = c(3, 4)), defining its dimensions as 3 rows and 4 columns. Finally, we use cat() for proper spacing and print the arrays with explanatory labels.

Creating an array Using matrix() function

matrix(data, nrow = ..., ncol = ..., byrow = FALSE, dimnames = NULL) 

• data: The data to be used in the matrix. It can be a vector or a list.
• nrow: Optional. The number of rows in the matrix. If not specified, it is determined from the length of the data.
• ncol: Optional. The number of columns in the matrix. If not specified, it is determined from the length of the data.
• byrow: Optional. A logical value indicating whether the matrix should be filled by rows (TRUE) or by columns (FALSE). Default is FALSE.
• dimnames: Optional. A list of length 2 containing the names for the rows and columns of the matrix. Default is NULL.

The below example shows how we can create an array using matrix() function

# Example 1: Creating a 2x3 matrix
matrix1 <- matrix(1:6, nrow = 2, ncol = 3)
cat("Example 1 - 2x3 Matrix:\n")
print(matrix1)

# Example 2: Creating a 3x2 matrix
matrix2 <- matrix(7:12, nrow = 3, ncol = 2)
cat("\nExample 2 - 3x2 Matrix:\n")
print(matrix2)

# Example 3: Creating a 4x4 matrix with repeating values
matrix3 <- matrix(rep(10, 16), nrow = 4, ncol = 4)
cat("\nExample 3 - 4x4 Matrix with Repeating Values:\n")
print(matrix3)

# Example 4: Creating a matrix with custom row names and column names
matrix4 <- matrix(letters[1:12], nrow = 3, ncol = 4, byrow = TRUE,
                  dimnames = list(c("Row1", "Row2", "Row3"),
                                   c("Col1", "Col2", "Col3", "Col4")))
cat("\nExample 4 - Matrix with Custom Row and Column Names:\n")
print(matrix4)

Output:

Example 1 - 2x3 Matrix:
     [,1] [,2] [,3]
[1,]    1    3    5
[2,]    2    4    6

Example 2 - 3x2 Matrix:
     [,1] [,2]
[1,]    7   10
[2,]    8   11
[3,]    9   12

Example 3 - 4x4 Matrix with Repeating Values:
     [,1] [,2] [,3] [,4]
[1,]   10   10   10   10
[2,]   10   10   10   10
[3,]   10   10   10   10
[4,]   10   10   10   10

Example 4 - Matrix with Custom Row and Column Names:
     Col1 Col2 Col3 Col4
Row1 "a"  "b"  "c"  "d" 
Row2 "e"  "f"  "g"  "h" 
Row3 "i"  "j"  "k"  "l"

In this approach, we are using the matrix() function in R to create arrays. Example 1 creates a 2x3 matrix with values 1 to 6, Example 2 creates a 3x2 matrix with values 7 to 12, and Example 3 creates a 4x4 matrix filled with the value 10. Example 4 demonstrates creating a matrix with custom row and column names, filled with letters from "a" to "l", arranged in 3 rows and 4 columns.