R: Extract or Replace Parts of a Factor

Extract.factor {base} | R Documentation

## Extract or Replace Parts of a Factor

### Description

Extract or replace subsets of factors.

### Usage

    ## S3 method for class 'factor'
    x[..., drop = FALSE]
    ## S3 method for class 'factor'
    x[[...]]
    ## S3 replacement method for class 'factor'
    x[...] <- value
    ## S3 replacement method for class 'factor'
    x[[...]] <- value

### Arguments

`x` | a factor
`...` | a specification of indices – see `Extract`.
`drop` | logical. If true, unused levels are dropped.
`value` | character: a set of levels. Factor values are coerced to character.

### Details

When unused levels are dropped the ordering of the remaining levels is preserved.

If `value` is not in `levels(x)`, a missing value is assigned with a warning.

Any `contrasts` assigned to the factor are preserved unless `drop = TRUE`.

The `[[` method supports argument `exact`.

### Value

A factor with the same set of levels as `x` unless `drop = TRUE`.

### See Also

`factor`, `Extract`.

### Examples

    ## following example(factor)
    (ff <- factor(substring("statistics", 1:10, 1:10), levels = letters))
    ff[, drop = TRUE]
    factor(letters[7:10])[2:3, drop = TRUE]

[Package base version 3.1.2 Index]