R: Row Indexes

row {base} | R Documentation

## Row Indexes

### Description

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

### Usage

    row(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 `i`.

### See Also

`col` to get columns.

### Examples

    x <- matrix(1:12, 3, 4)
    # extract the diagonal of a matrix
    dx <- x[row(x) == col(x)]
    dx

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

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