R: factor levels, recode rest to 'other'

Question

I use factors somewhat infrequently and generally find them comprehensible, but I often am fuzzy about the details for specific operations. Currently, I am coding/collapsing cat

Answer 1

You can use forcats::fct_other():

library(forcats)
data$naics <- fct_other(data$naics, keep = top8, other_level = 'other')

Or using fct_other() as a part of a dplyr::mutate():

library(dplyr)
data <- mutate(data, naics = fct_other(naics, keep = top8, other_level = 'other')) 

data %>% head(10)
   employees  naics
1        420  other
2        264  other
3        189  other
4        157 621610
5        376 621610
6        236  other
7        658 621320
8        959 621320
9        216  other
10       156  other

Note that if the argument other_level is not set, the other levels default to 'Other' (uppercase 'O').

And conversely, if you had a only a few factors you wanted converted to 'other', you could use the argument drop instead:

data %>%  
  mutate(keep_fct = fct_other(naics, keep = top8, other_level = 'other'),
         drop_fct = fct_other(naics, drop = top8, other_level = 'other')) %>% 
  head(10)

   employees  naics keep_fct drop_fct
1        474 621491    other   621491
2        805 621111   621111    other
3        434 621910    other   621910
4        845 621111   621111    other
5        243 621340    other   621340
6        466 621493    other   621493
7        369 621111   621111    other
8         57 621493    other   621493
9        144 621491    other   621491
10       786 621910    other   621910

dpylr also has recode_factor() where you can set the .default argument to other, but with a larger number of levels to recode, like with this example, could be tedious:

data %>% 
   mutate(naices = recode_factor(naics, `621111` = '621111', `621210` = '621210', `621399` = '621399', `621610` = '621610', `621330` = '621330', `621310` = '621310', `621511` = '621511', `621420` = '621420', `621320` = '621320', .default = 'other'))