| Extract.factor {base} | R Documentation |
Extract or Replace Parts of a Factor
Description
Extract or replace subsets of factors.
Usage
x[i, drop = FALSE]
x[i] <- value
Arguments
x |
a factor |
i |
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. |
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.
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]