Apply a lumping to an ordinal variable

Transforms ordered categorical data by combining its levels according to a given lumping. The order of the entries of the lumping defines the order of the new levels, from lowest to highest. This makes it possible to reuse a lumping, for example one learned on training data, on new data.

Usage

apply_ordinal_lumping(data, lumping, level_namer = default_level_namer)

Arguments

data

Factor or character vector of the categorical data. If data is an ordered factor, the lumping must respect its level order.

lumping

Named list of character vectors, where each vector contains the original levels that are combined into a new level named after the entry. If the list is unnamed, names are generated with level_namer.

level_namer

Function that takes a character vector of the original levels in a lump and returns the name of the new lumped level. Only used when lumping is unnamed. Default: concatenating the original levels with a "+" in between.

Value

An ordered factor vector with the lumped levels.

Details

Levels that appear in the lumping but not in the data are kept as empty levels, so that applying the same lumping always yields the same factor levels. Conversely, levels that appear in the data but not in the lumping are replaced by NA, with a warning.

See also

lump_ordinal() to find and apply the optimal lumping in one step.

apply_nominal_lumping() for the nominal analogue of this function.

Author

Daan Koning

Examples

risk_group <- c("low", "high", "medium", "low", "very high")
lumping <- list("low" = "low", "medium+" = c("medium", "high", "very high"))
apply_ordinal_lumping(risk_group, lumping)
#> [1] low     medium+ medium+ low     medium+
#> Levels: low < medium+