R – Get Multiple Rows of Matrix
To get multiple rows of matrix, specify the row numbers as a vector followed by a comma, in square brackets, after the matrix variable name. This expression returns the required rows as a matrix.
In this tutorial, we will learn how to get a multiple rows from a Matrix, with examples.
Syntax
The syntax of the expression to get multiple rows at given vector of positions/indices in a matrix is
X[rows, ]
where
| Argument | Description |
|---|---|
| X | A matrix. |
| rows | A vector of row numbers. |
Return Value
The expression returns the selected rows as a matrix from matrix X at given rows numbers.
Examples
In the following program, we create a matrix and get the rows at position 1 and 3. We pass the vector c(1, 3) for the rows in the expression X[rows, ].
example.R
data <- c(2, 4, 7, 5, 10, 8, 1, 3, 5)
A <- matrix(data, nrow = 3)
rows <- A[c(1,3), ]
print("Matrix A")
print(A)
print("Selected Rows")
print(rows) Output
[1] "Matrix A"
[,1] [,2] [,3]
[1,] 2 5 1
[2,] 4 10 3
[3,] 7 8 5
[1] "Selected Rows"
[,1] [,2] [,3]
[1,] 2 5 1
[2,] 7 8 5 If any of the row numbers is out of bounds for given matrix, then R throws Error “subscript out of bounds”.
Let us try to get a rows at rows = c(1, 2, 5), where the matrix has only 3 rows. Since row 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, 5) A <- matrix(data, nrow = 3) rows <- 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 rows of a Matrix at given row positions in R, with the help of examples.