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]

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