recipes (version 0.1.7)

discretize: Discretize Numeric Variables

Description

discretize converts a numeric vector into a factor with bins having approximately the same number of data points (based on a training set).

Usage

discretize(x, ...)
# S3 method for default
discretize(x, ...)
# S3 method for numeric
discretize(x, cuts = 4, labels = NULL,
  prefix = "bin", keep_na = TRUE, infs = TRUE, min_unique = 10,
  ...)
# S3 method for discretize
predict(object, new_data, ...)

Arguments

x

A numeric vector

...

Options to pass to stats::quantile() that should not include x or probs.

cuts

An integer defining how many cuts to make of the data.

labels

A character vector defining the factor levels that will be in the new factor (from smallest to largest). This should have length cuts+1 and should not include a level for missing (see keep_na below).

prefix

A single parameter value to be used as a prefix for the factor levels (e.g. bin1, bin2, ...). If the string is not a valid R name, it is coerced to one.

keep_na

A logical for whether a factor level should be created to identify missing values in x.

infs

A logical indicating whether the smallest and largest cut point should be infinite.

min_unique

An integer defining a sample size line of dignity for the binning. If (the number of unique values)/(cuts+1) is less than min_unique, no discretization takes place.

object

An object of class discretize.

new_data

A new numeric object to be binned.

Value

discretize returns an object of class discretize and predict.discretize returns a factor vector.

Details

discretize estimates the cut points from x using percentiles. For example, if cuts = 3, the function estimates the quartiles of x and uses these as the cut points. If cuts = 2, the bins are defined as being above or below the median of x.

The predict method can then be used to turn numeric vectors into factor vectors.

If keep_na = TRUE, a suffix of "_missing" is used as a factor level (see the examples below).

If infs = FALSE and a new value is greater than the largest value of x, a missing value will result.

Examples

# NOT RUN {
data(biomass)

biomass_tr <- biomass[biomass$dataset == "Training",]
biomass_te <- biomass[biomass$dataset == "Testing",]

median(biomass_tr$carbon)
discretize(biomass_tr$carbon, cuts = 2)
discretize(biomass_tr$carbon, cuts = 2, infs = FALSE)
discretize(biomass_tr$carbon, cuts = 2, infs = FALSE, keep_na = FALSE)
discretize(biomass_tr$carbon, cuts = 2, prefix = "maybe a bad idea to bin")

carbon_binned <- discretize(biomass_tr$carbon)
table(predict(carbon_binned, biomass_tr$carbon))

carbon_no_infs <- discretize(biomass_tr$carbon, infs = FALSE)
predict(carbon_no_infs, c(50, 100))

rec <- recipe(HHV ~ carbon + hydrogen + oxygen + nitrogen + sulfur,
              data = biomass_tr)
rec <- rec %>% step_discretize(carbon, hydrogen)
rec <- prep(rec, biomass_tr)
binned_te <- bake(rec, biomass_te)
table(binned_te$carbon)
# }