Multidimensional Array in R

Arrays are the R data objects which can store data in more than two dimensions. For example: If we create an array of dimensions (2, 3, 4) then it creates 4 rectangular matrices each with 2 rows and 3 columns. These types of arrays are called Multidimensional Arrays. Arrays can store only data types.

Creating a Multidimensional Array

An array is created using the array() function. It takes vectors as input and uses the values in the dim parameter to create an array. A multidimensional array can be created by defining the value of ‘dim‘ argument as the number of dimensions that are required.

Syntax:

MArray = array(c(vec1, vec2), dim)

Examples:

# Create two vectors of different lengths.
vector1 <- c(5, 9, 3)
vector2 <- c(10, 11, 12, 13, 14, 15)

# Take these vectors as input to the array.
result <- array(c(vector1, vector2), dim = c(3, 3, 2))
print(result)

Output:

, , 1

     [,1] [,2] [,3]
[1,]    5   10   13
[2,]    9   11   14
[3,]    3   12   15

, , 2

     [,1] [,2] [,3]
[1,]    5   10   13
[2,]    9   11   14
[3,]    3   12   15

Naming Columns and Rows

We can give names to the rows, columns, and matrices in the array by using the dimnames parameter.

Example:

# Create two vectors of different lengths.
vector1 <- c(5, 9, 3)
vector2 <- c(10, 11, 12, 13, 14, 15)
column.names <- c("COL1", "COL2", "COL3")
row.names <- c("ROW1", "ROW2", "ROW3")
matrix.names <- c("Matrix1", "Matrix2")

# Take these vectors as input to the array.
result <- array(c(vector1, vector2), dim = c(3, 3, 2),
                  dimnames = list(row.names, column.names,
                  matrix.names))
print(result)

Output:

, , Matrix1

     COL1 COL2 COL3
ROW1    5   10   13
ROW2    9   11   14
ROW3    3   12   15

, , Matrix2

     COL1 COL2 COL3
ROW1    5   10   13
ROW2    9   11   14
ROW3    3   12   15

Manipulating Array Elements

As the array is made up of matrices in multiple dimensions, the operations on elements of the array are carried out by accessing elements of the matrices. There are various different Operations can be performed on Arrays.

Example:

# Create two vectors of different lengths.
vector1 <- c(5, 9, 3)
vector2 <- c(10, 11, 12, 13, 14, 15)

# Take these vectors as input to the array.
array1 <- array(c(vector1, vector2), dim = c(3, 3, 2))

# Create two vectors of different lengths.
vector3 <- c(9, 1, 0)
vector4 <- c(6, 0, 11, 3, 14, 1, 2, 6, 9)
array2 <- array(c(vector1, vector2), dim = c(3, 3, 2))

# create matrices from these arrays.
matrix1 <- array1[,,2]
matrix2 <- array2[,,2]

# Add the matrices.
result <- matrix1 + matrix2
print(result)

Output:

     [,1] [,2] [,3]
[1,]   10   20   26
[2,]   18   22   28
[3,]    6   24   30