row: Row Indexes

Description

Returns a matrix of integers indicating their row number in a matrix-like object, or a factor indicating the row labels.

Usage

row(x, as.factor = FALSE)

Arguments

a matrix-like object, that is one with a two-dimensional dim.

as.factor

a logical value indicating whether the value should be returned as a factor of row labels (created if necessary) rather than as numbers.

Value

An integer (or factor) matrix with the same dimensions as x and whose ij-th element is equal to i (or the i-th row label).

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

Examples

Run this code

x <- matrix(1:12, 3, 4)
# extract the diagonal of a matrix
dx <- x[row(x) == col(x)]
dx

# create an identity 5-by-5 matrix
x <- matrix(0, nrow = 5, ncol = 5)
x[row(x) == col(x)] <- 1
x

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