Special grouping number for each pairs

Question

There is already some part of the question answered here special-group-number-for-each-combination-of-data. In most cases we have pairs and other data values inside the data. Wh

Answer 1

Here are two approaches which reproduce OP's expected result for the given sample dataset.`

Both work in the same way. First, all "disturbing" rows, i.e., rows which do not contain "valid" names, are skipped and the rows with "valid" names are simply numbered in groups of 2. Second, the rows with exempt names are given the special group number. Finally, the NA rows are filled by carrying the last observation forward.

data.table

library(data.table)
names <- c(c("bad","good"),1,2,c("good","bad"),111,c("bad","J.James"),c("good","J.James"),333,c("J.James","good"),761,'Veni',"vidi","Vici")
exempt <- c("Veni", "vidi", "Vici")
data.table(names)[is.na(as.numeric(names)) & !names %in% exempt, 
                  grp := rep(1:.N, each = 2L, length.out = .N)][
                    names %in% exempt, grp := 666L][
                      , grp := zoo::na.locf(grp)][]

      names grp
 1:     bad   1
 2:    good   1
 3:       1   1
 4:       2   1
 5:    good   2
 6:     bad   2
 7:     111   2
 8:     bad   3
 9: J.James   3
10:    good   4
11: J.James   4
12:     333   4
13: J.James   5
14:    good   5
15:     761   5
16:    Veni 666
17:    vidi 666
18:    Vici 666

dplyr/tidyr

Here is my attempt to provide a dplyr/tidyr solution:

library(dplyr)
as_tibble(names) %>% 
  mutate(grp = if_else(is.na(as.numeric(names)) & !names %in% exempt,  
                       rep(1:n(), each = 2L, length.out = n()),
                       if_else(names %in% exempt, 666L, NA_integer_))) %>% 
  tidyr::fill(grp)

# A tibble: 18 x 2
   value     grp
   <chr>   <int>
 1 bad         1
 2 good        1
 3 1           1
 4 2           1
 5 good        3
 6 bad         3
 7 111         3
 8 bad         4
 9 J.James     5
10 good        5
11 J.James     6
12 333         6
13 J.James     7
14 good        7
15 761         7
16 Veni      666
17 vidi      666
18 Vici      666