How to Access Matrix Elements using Indexing and Slicing in R - Step by Step Examples

How to Access Matrix Elements using Indexing and Slicing in R ?

Answer

To access matrix elements using indexing and slicing in R, you can use square brackets [] with row and column indices. R uses 1-based indexing, so the first element is at position [1,1]. You can also use slicing to access submatrices by specifying ranges of rows and columns.

✐ Examples

1 Accessing a Single Element

In this example,

We create a matrix named matrix with values from 1 to 9 arranged in 3 rows and 3 columns using the matrix() function.
The matrix() function takes a vector of values and the arguments nrow and ncol to specify the number of rows and columns respectively.
We access a single element by specifying its row and column indices within square brackets. For example, matrix[2, 3] accesses the element in the 2nd row and 3rd column of matrix.
We store the accessed element in a variable named element and print it to standard output.

R Program

matrix <- matrix(1:9, nrow = 3, ncol = 3)
element <- matrix[2, 3]
print(element)

Output

[1] 6

2 Accessing a Row

In this example,

We create a matrix named matrix with values from 1 to 12 arranged in 3 rows and 4 columns using the matrix() function.
The matrix() function takes a vector of values and the arguments nrow and ncol to specify the number of rows and columns respectively.
We access an entire row by specifying its row index and leaving the column index blank. For example, matrix[1, ] accesses all the elements in the 1st row of matrix.
We store the accessed row in a variable named row and print it to standard output.

R Program

matrix <- matrix(1:12, nrow = 3, ncol = 4)
row <- matrix[1, ]
print(row)

Output

[1] 1 4 7 10

3 Accessing a Submatrix

In this example,

We create a matrix named matrix with values from 1 to 16 arranged in 4 rows and 4 columns using the matrix() function.
The matrix() function takes a vector of values and the arguments nrow and ncol to specify the number of rows and columns respectively.
We access a submatrix by specifying ranges of row and column indices. For example, matrix[2:4, 2:4] accesses the elements in rows 2 to 4 and columns 2 to 4 of matrix.
We store the accessed submatrix in a variable named submatrix and print it to standard output.

R Program

matrix <- matrix(1:16, nrow = 4, ncol = 4)
submatrix <- matrix[2:4, 2:4]
print(submatrix)

Output

     [,1] [,2] [,3]
[1,]    6   10   14
[2,]    7   11   15
[3,]    8   12   16

Summary

In this tutorial, we learned How to Access Matrix Elements using Indexing and Slicing in R language with well detailed examples.

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How to Access Matrix Elements using Indexing and Slicing in R - Step by Step Examples

How to Access Matrix Elements using Indexing and Slicing in R ?

Answer

✐ Examples

1 Accessing a Single Element

R Program

Output

2 Accessing a Row

R Program

Output

3 Accessing a Submatrix

R Program

Output

Summary

More R Matrices Tutorials