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

[Package

*base* version 2.2.1

Index]