R: Row Indexes

row {base} | R Documentation

## Row Indexes

### Description

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

### Usage

    row(x, as.factor = FALSE)
    .row(dim)

### Arguments

`x` | a matrix-like object, that is one with a two-dimensional `dim`.
`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 row 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 `i` (or the `i`-th row label).

### References

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

### See Also

`col` to get columns; `slice.index` for a general way to get slice indices in an array.

### Examples

    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"

[Package base version 4.0.5 Index]