Map array of strings to an array of integers

Question

Suppose I have a column in a data frame as colors say c(\"Red\", \"Blue\", \"Blue\", \"Orange\"). I would like to get it as c(1,2,2,3).

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Answer 1

Here is a function based on previous code:

# Recode 'string' into 'integer'
recode_str_int <- function(df, feature) {

  # 1. Unique values

  # 1.1. 'string' values
  list_str <- sort(unique(df[, feature]))

  # 1.2. 'integer' values
  list_int <- 1:length(list_str)

  # 2. Create new feature

  # 2.1. Names
  names(list_int) = list_str
  df$feature_new = list_int[df[, feature]]

  # 3. Result
  df$feature_new

} # recode_str_int

Call it like:

 df$new_feature <- recode_str_int(df, "feature")