I have a data frame with 5 indicators per site. I calculated the reciprocal of 2 of the indicators, and then minmax scaled all 5 indicators. Now I would like to restore them to their original values. I managed to get it right, but only for the indicators for which I originally did not calculate reciprocals. Could you help me to find where the error is? Here is a reproducible example:

# Load necessary libraries
library(dplyr)

# Step 1: Create the example dataframe
set.seed(1)
df <- data.frame(
  Region = rep(c("Region1", "Region2"), each = 5),
  Site = rep(1:5, times = 2),
  Indicator_A = sample(1:100, 10, replace = TRUE),
  Indicator_B = sample(1:100, 10, replace = TRUE),
  Indicator_C = sample(0:1000, 10, replace = TRUE),
  Indicator_D = sample(5:500, 10, replace = TRUE),
  Indicator_E = sample(-10:10, 10, replace = TRUE)
)

# define minmax function
norm_minmax <- function(x, na.rm = FALSE) {
  (x - min(x, na.rm = na.rm)) / (max(x, na.rm = na.rm) - min(x, na.rm = na.rm))
}

df_scaled <- 
  df %>% 
  
  # calculate reciprocal of selected indicators  
  mutate(
    across(
      c(Indicator_A, Indicator_B),
      ~ 1 / .)) %>% 
  
  # min-max scale variables per region
  mutate(
    across(
      where(is.numeric),
      ~ norm_minmax(., na.rm = TRUE)),
    .by = Region) 

# revert transformations

# define undo minmax function

undo_minmax <- function(scaled, unscaled, na.rm = FALSE) {
  unscaled_min <- min(unscaled, na.rm = na.rm)
  unscaled_range <- max(unscaled, na.rm = na.rm) - unscaled_min
  original <- scaled * unscaled_range + unscaled_min
  return(original)
}

df_restored <-
  df_scaled %>% 
  filter(Region == "Region1") %>% 
  
  # undo minmax scaling
  mutate(
    across(
      c(Indicator_A:Indicator_E),
      ~ undo_minmax(scaled = .x, 
                    unscaled = df[df$Region == "Region1",][[cur_column()]], 
                    na.rm = TRUE))) %>% 
  
  # calculate reciprocal of reciprocals
  mutate(across(c(Indicator_A, Indicator_B), ~ 1/.)) %>%
  
  # reclassify inf values as 0 resulting from dividing 1/0
  mutate(across(c(Indicator_A, Indicator_B),
                ~ if_else(is.infinite(.), 0, .)))  

all.equal(df_restored, df %>% filter(Region == "Region1"))
print(df_restored)
print(df[df$Region == "Region1", ])