A demonstration of mutate_at

demo_mutate_at

library(tidyverse)

# values to mimic 1 to 7 rating scale with 99 as missing
values <- c(1:7, 99)

# for reproducibility
set.seed(0215)

# example data frame with two variables
dat <- tibble("A_1" = sample(values, 10, replace = T),
              "A_2" = sample(values, 10, replace = T))

# view example data
dat

# in original variable names, re-code 99 to missing
# for this example you could use mutate_all, but I generally
# use mutate_at to specify variables
dat %>%
  mutate_at(vars(matches("A")), na_if, 99)


# create new variables with re-coded values
# the name of the function in list assigns a name to the new variable
dat %>%
  mutate_at(vars(matches("A")), list(clean = ~ na_if(., 99)))

# you can use this with multiple steps to track a data cleaning process
# a top 2 box is a score of 6 or 7 on a 1-7 rating scale
dat %>%
  mutate_at(vars(matches("A")), list(clean = ~ na_if(., 99))) %>%
  mutate_at(vars(matches("clean")), list(
    box = ~ case_when(is.na(.)   ~ NA_character_,
                      . %in% 6:7 ~ "top 2",
                      . %in% 1:5 ~ "other")
  ))