Extract.factor {base} | R Documentation |
Extract or replace subsets of factors.
## 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
x |
a factor |
... |
a specification of indices – see |
drop |
logical. If true, unused levels are dropped. |
value |
character: a set of levels. Factor values are coerced to character. |
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
.
A factor with the same set of levels as x
unless drop = TRUE
.
## following example(factor) (ff <- factor(substring("statistics", 1:10, 1:10), levels = letters)) ff[, drop = TRUE] factor(letters[7:10])[2:3, drop = TRUE]