library(vtreat)

# making dataset
set.seed(123)
data <- data.frame(
  x1 = c('a', 'b', 'a', 'c', 'b', 'a'),  # categorical variable
  x2 = c(10, 20, 30, 40, 50, NA),        # nemrical variable
  y = c(1, 0, 1, 0, 1, 0)                # response variable(classification)
)

# Treatment plan
treatment_plan <- vtreat::designTreatmentsC(
  dframe = data,
  varlist = c("x1", "x2"),  # explanatory variable
  outcomename = "y",        # response variable
  outcometarget = 1         # (1 = positive class, usually success=1)
)

# data preparation
prepared_data <- vtreat::prepare(treatment_plan, data)

print(prepared_data)