Returns a matrix of integers indicating their row number in a
matrix-like object, or a factor indicating the row labels.
row(x, as.factor = FALSE)
a matrix-like object, that is one with a two-dimensional
a logical value indicating whether the value should
be returned as a factor of row labels (created if necessary)
rather than as numbers.
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).
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
The New S Language.
Wadsworth & Brooks/Cole.
col to get columns.
x <- matrix(1:12, 3, 4)
# extract the diagonal of a matrix
dx <- x[row(x) == col(x)]
# create an identity 5-by-5 matrix
x <- matrix(0, nrow = 5, ncol = 5)
x[row(x) == col(x)] <- 1
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