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 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.
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