How to get multiple Columns of Matrix in R?

R – Get Multiple Columns of Matrix

To get multiple columns of matrix, specify the column numbers as a vector preceded by a comma, in square brackets, after the matrix variable name. This expression returns the required columns as a matrix.

In this tutorial, we will learn how to get a multiple columns from a Matrix, with examples.

Syntax

The syntax of the expression to get multiple columns at given vector of positions/indices in a matrix is

X[, columns]

where

Argument	Description
X	A matrix.
columns	A vector of column numbers.

Return Value

The expression returns the selected columns as a matrix from matrix X at given columns numbers.

Examples

In the following program, we create a matrix and get the columns at position 1 and 3. We pass the vector c(1, 3) for the columns in the expression X[, columns].

example.R

data <- c(2, 4, 7, 5, 10, 8, 1, 3)
A <- matrix(data, nrow = 2)
columns <- A[, c(1, 3)]

print("Matrix A")
print(A)
print("Selected Columns")
print(columns)

Output

[1] "Matrix A"
     [,1] [,2] [,3] [,4]
[1,]    2    7   10    1
[2,]    4    5    8    3
[1] "Selected Columns"
     [,1] [,2]
[1,]    2   10
[2,]    4    8

If any of the column numbers is out of bounds for given matrix, then R throws Error “subscript out of bounds”.

Let us try to get a columns at columns = c(1, 2, 5), where the matrix has only 4 rows. Since column number 5 is out of bounds for the given matrix, R must throw the error.

example.R

data <- c(2, 4, 7, 5, 10, 8, 1, 3)
A <- matrix(data, nrow = 2)
columns <- A[, c(1, 2, 5)]

Output

Error in A[, c(1, 2, 5)] : subscript out of bounds

Conclusion

In this R Tutorial, we learned how to get multiple columns of a Matrix at given column positions in R, with the help of examples.