col {base}R Documentation

Column Indexes

Description

Returns a matrix of integers indicating their column number in the matrix.

Usage

col(x, as.factor=FALSE)

Arguments

x a matrix.
as.factor a logical value indicating whether the value should be returned as a factor rather than as numeric.

Value

An integer matrix with the same dimensions as x and whose ij-th element is equal to j.

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, nr = 5, nc = 5)
x[row(x) == col(x)] <- 1
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