Returns a matrix of integers indicating their row number in a matrix-like object, or a factor indicating the row labels.
a matrix-like object, that is one with a two-dimensional
a matrix dimension, i.e., an integer valued numeric vector of length two (with non-negative entries).
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;
slice.index for a general way to get slice indices
in an array.
1 2 3 4 5 6 7 8 9 10 11 12
x <- matrix(1:12, 3, 4) # extract the diagonal of a matrix - more slowly than diag(x) dx <- x[row(x) == col(x)] dx # create an identity 5-by-5 matrix more slowly than diag(n = 5): x <- matrix(0, nrow = 5, ncol = 5) x[row(x) == col(x)] <- 1 x (i34 <- .row(3:4)) stopifnot(identical(i34, .row(c(3,4)))) # 'dim' maybe "double"
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