Encode categorical variables

Turns categorical columns into the numeric columns a model needs. Dummy coding is one indicator per level, with no reference level dropped; effect coding drops the last level's indicator and codes that level -1 across the remaining columns; factor coding leaves one factor column.

Usage

encode_factors(
  data,
  variables,
  coding = c("factor", "dummy", "effect"),
  labels = NULL,
  prefix = "f_",
  replace = FALSE
)

Arguments

data

Base data.frame, or a simulab_sim.

variables

Categorical variables to encode. A character vector of at least one column name of data. Levels are taken in the order factor() sorts them.

coding

Encoding to apply, one of "factor" (the default), one factor column named <prefix><variable>, "dummy", one 0/1 indicator per level named <prefix><variable>_<level>, or "effect", the same indicators without the last level's column and with -1 in every column for that level.

labels

Optional replacement level labels, as a named list per variable, one atomic vector shared by every variable, or a tidy data frame with columns variable, level and label. Defaults to NULL, the values as they stand. The labels are passed to factor(), so they rename the levels in sorted order and also feed the generated column names.

prefix

Prefix for generated variables. A single string, defaulting to "f_".

replace

Remove the source variables after encoding. A single flag, defaulting to FALSE.

Value

A simulab_sim base data.frame with the columns of data, minus the source variables when replace is TRUE, followed by the generated columns, one row per input row. The component encoding, reached with as.data.frame(x, what = "encoding"), holds one row per generated column with columns source, encoded and coding.

Examples

data <- data.frame(id = 1:6, arm = rep(c("a", "b", "c"), each = 2))
encode_factors(data, variables = "arm", coding = "dummy")
#> <simulab_sim:encoded_factors> 6 rows x 5 columns
#>   id arm f_arm_a f_arm_b f_arm_c
#> 1  1   a       1       0       0
#> 2  2   a       1       0       0
#> 3  3   b       0       1       0
#> 4  4   b       0       1       0
#> 5  5   c       0       0       1
#> 6  6   c       0       0       1
#> 
#> Other tables: encoding. Read one with as.data.frame(x, what = "encoding").