How to use dplyr to convert variables from numeric to factor with unique levels

Question

I am trying to convert a large number of numeric variables into factor variables using a 'codebook' of factor levels (formatted as a list of named lists). I can do this one by one using mutate() and recode_factor() , but would like to do them all in one go using mutate_at() . How might I go about this?

codebook <- list(
  vs = list(`0` = 'V-shaped',
            `1` = 'straight'),
  am = list(`0` = 'automatic',
            `1` = 'manual')
)

mtcars %>%
  mutate(vs = recode_factor(vs, levels = !!!(pluck(codebook, 'vs'))))

mtcars %>%
  mutate_at(vars(names(codebook)),
            funs(recode_factor(., levels = !!!(pluck(codebook, 'somehow_pass_column_name_here?')))))

Answer 1

One option would be to loop through the names of the 'codebook'

library(tidyverse)
names(codebook) %>%
   map(~ mtcars %>% 
           transmute(!! .x := recode_factor(!! rlang::sym(.x), 
                        levels  = !!!(pluck(codebook, .x))))) %>% 
   bind_cols(mtcars %>%
   select(-one_of(names(codebook))), .)

---

or use a for loop

library(magrittr)
for(nm in names(codebook)) {
  mtcars %<>%
        mutate(!! nm := recode_factor(!! rlang::sym(nm), 
               levels = !!!(pluck(codebook, nm))))
}

Answer 2

You could still use mutate for multiple variables, unless that's what you meant by one-by-one. I'm not well versed on mutate_at , so maybe someone knows that method.

mtcars %>%
  mutate(vs = recode_factor(vs, levels = !!!(pluck(codebook, 'vs'))),
         am = recode_factor(am, levels = !!!(pluck(codebook, 'am'))))

    mpg cyl  disp  hp drat    wt  qsec       vs        am gear carb
1  21.0   6 160.0 110 3.90 2.620 16.46 V-shaped    manual    4    4
2  21.0   6 160.0 110 3.90 2.875 17.02 V-shaped    manual    4    4
3  22.8   4 108.0  93 3.85 2.320 18.61 straight    manual    4    1
4  21.4   6 258.0 110 3.08 3.215 19.44 straight automatic    3    1
5  18.7   8 360.0 175 3.15 3.440 17.02 V-shaped automatic    3    2
6  18.1   6 225.0 105 2.76 3.460 20.22 straight automatic    3    1
7  14.3   8 360.0 245 3.21 3.570 15.84 V-shaped automatic    3    4
8  24.4   4 146.7  62 3.69 3.190 20.00 straight automatic    4    2
9  22.8   4 140.8  95 3.92 3.150 22.90 straight automatic    4    2
10 19.2   6 167.6 123 3.92 3.440 18.30 straight automatic    4    4