base (version 3.2.1)

col: Column Indexes

Description

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

Usage

col(x, as.factor = FALSE)

Arguments

x

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 column 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 j (or the j-th column label).

References

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

See Also

row to get rows.

Examples

# extract an off-diagonal of a matrix
ma <- matrix(1:12, 3, 4)
ma[row(ma) == col(ma) + 1]

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