R: Column Indexes (original) (raw)
| col {base} | R Documentation |
|---|
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)
.col(dim)
Arguments
| x | a matrix-like object, that is one with a two-dimensionaldim. |
|---|---|
| dim | a matrix dimension, i.e., an integer valued numeric vector of length two (with non-negative entries). |
| 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 whoseij-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](../../base/help/row.html) to get rows;[slice.index](../../base/help/slice.index.html) for a general way to get slice indices in an array.
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 more slowly than diag(n = 5):
x <- matrix(0, nrow = 5, ncol = 5)
x[row(x) == col(x)] <- 1
(i34 <- .col(3:4))
stopifnot(identical(i34, .col(c(3,4)))) # 'dim' maybe "double"
[Package _base_ version 4.6.0 Index]