Extract or replace subsets of factors.
# S3 method for factor
[(x, …, drop = FALSE)
# S3 method for factor
[[(x, …)
# S3 method for factor
[(x, …) <- value
# S3 method for factor
[[(x, …) <- value
a factor
a specification of indices -- see Extract
.
logical. If true, unused levels are dropped.
character: a set of levels. Factor values are coerced to character.
A factor with the same set of levels as x
unless drop = TRUE
.
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
.
# 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] # }
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