factor() along with cheaper utilitiesA fast version of factor() using the collapse package.
There are some additional utilities, most of which begin with the prefix
'levels_', such as
as_factor() which is an efficient way to coerce both vectors and factors,
levels_factor() which returns the levels of a factor, as a factor,
levels_used() which returns the used levels of a factor,
levels_unused() which returns the unused levels of a factor,
levels_add_na() which adds an explicit NA level,
levels_drop_na() which drops the NA level,
levels_drop() which drops unused factor levels,
and finally levels_reorder() which reorders the levels of x
based on y using the ordered median values of y for each level.
factor_(
x = integer(),
levels = NULL,
order = TRUE,
na_exclude = TRUE,
ordered = is.ordered(x)
)as_factor(x)
levels_factor(x)
levels_used(x)
levels_unused(x)
used_levels(x)
unused_levels(x)
levels_add_na(x, name = NA, where = c("last", "first"))
levels_drop_na(x)
levels_drop(x)
levels_reorder(x, order_by, decreasing = FALSE)
A factor or character in the case of levels_used and levels_unused.
A vector.
Optional factor levels.
Should factor levels be sorted? Default is TRUE.
It typically is faster to set this to FALSE, in which case the levels
are sorted by order of first appearance.
Should NA values be excluded from the factor levels?
Default is TRUE.
Should the result be an ordered factor?
Name of NA level.
Where should NA level be placed? Either first or last.
A vector to order the levels of x by using the medians of
order_by.
Should the reordered levels be in decreasing order?
Default is FALSE.
This operates similarly to collapse::qF().
The main difference internally is that collapse::funique() is used
and therefore s3 methods can be written for it.
Furthermore, for date-times factor_ differs in that it differentiates
all instances in time whereas factor differentiates calendar times.
Using a daylight savings example where the clocks go back:
factor(as.POSIXct(1729984360, tz = "Europe/London") + 3600 *(1:5))
produces 4 levels whereas
factor_(as.POSIXct(1729984360, tz = "Europe/London") + 3600 *(1:5))
produces 5 levels.