# Extract.factor

##### Extract or Replace Parts of a Factor

Extract or replace subsets of factors.

- Keywords
- category

##### Usage

```
# S3 method for factor
[(x, …, drop = FALSE)
# S3 method for factor
[[(x, …)
# S3 method for factor
[(x, …) <- value
# S3 method for 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

##### Examples

`library(base)`

```
# NOT RUN {
## following example(factor)
(ff <- factor(substring("statistics", 1:10, 1:10), levels = letters))
ff[, drop = TRUE]
factor(letters[7:10])[2:3, drop = TRUE]
# }
```

*Documentation reproduced from package base, version 3.4.3, License: Part of R 3.4.3*

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