Add quantile with rename function

[karissawhiting]

add_ntile <- function(df, percentile, variable) {
  # Determine the number of tiles based on the percentile type
  ntiles <- switch(
    percentile,
    "median" = 2,
    "tertile" = 3,
    "quantile" = 4,
    stop("Choose 'median', 'tertile', or 'quantile'")
  )
  
  # Compute quantile breaks for the variable
  breaks <- quantile(df[[variable]],
                     probs = seq(0, 1, length.out = ntiles + 1),
                     na.rm = TRUE)
  
  # Cut the variable into the specified percentiles
  percentiles <- cut(df[[variable]], breaks = breaks, include.lowest = TRUE)
  
  # Rename the levels
  new_levels <- glue::glue("{percentile} {1:ntiles}: {levels(percentiles)}")
  levels(percentiles) <- new_levels
  
  # Add the new percentile column to the data frame
  var_name_to_add <- 
    as.character(glue::glue("{variable}_{percentile}"))

  df <- df %>%
    mutate(!!var_name_to_add := percentiles)

  return(df)
}