How to create factor with mutate with levels coming from another col

Question

I have this df:

city	code
PR	41
SC	42
RS	43

I want to change city to factor, but keep the order as in the code. If I only do

df %>% mutate(city= factor(city))

it orders alphabetically.

I would like something such as

df %>% mutate(city= factor(city, levels = code))

Thanks!

EDIT: I don't want to do manually levels = c('PR', 'SC', 'RS') because it has many more categories!

Answer 1

We may use levels = unique(city)) as unique gets the unique elements in the order of occurrence of the elements

library(dplyr)
df <- df %>%
     mutate(city = factor(city, levels = unique(city)))

---

If we want to reorder based on a different column, use fct_reorder

library(forcats)
df <- df %>%
    mutate(city = fct_reorder(city, code))

-checking

levels(df$city)
[1] "PR" "SC" "RS"

data

df <- structure(list(city = c("PR", "SC", "RS"), code = 41:43), 
class = "data.frame", row.names = c(NA, 
-3L))