From a list of list to tibble in long format

I have this list of lists:

regions <- list(c("AO", "BI", "BW", "DJ", "DZ", "ET", "GH", "GM", "KE", "LS", "MA", "MR", "MW", "MZ", "NG", "SL", "SZ", "TN", "TZ", "UG", "ZA", "ZM", "ZR", "ZW"),
           c("BD", "CN", "HK", "ID", "IN", "KR", "MU", "MY", "PH", "PK", "SG", "TH", "TW", "VN", "AU", "NZ"),
           c("AT", "BA", "BE", "BL", "CH", "CI", "CT", "CY", "CZ", "DE", "DK", "EO", "ES", "EU", "FI", "FR", "GA", "GB", "GG", "GR", "HU", "IC", "IE", "IT", "JR", "KZ", "LN", "LU", "LV", "MK", "MT", "NL", "NO", "PO", "PT", "RM", "RS", "RU", "SE", "SJ", "SX", "TR", "UR"),
           c("AD", "AE", "BH", "DU", "EG", "IQ", "IR", "IS", "JO", "KW", "LB", "OM", "PS", "QA", "SA", "SY", "YE"),
           c("CA", "KY", "US"),
           c("AR", "BR", "CB", "CL", "EC", "MX", "PA", "PE", "PY", "UY", "VE"),
           c("JP"))

There are 7 lists, and I would like this data in a tibble format, with a region ID for each list:

country | region_id

"AO"   |   1

"BI"   |   1

"BW"   |   1

...

"BD"   |   2

"CN"   |   2

"HK"   |   2

…

>Solution :

Use enframe + unnest:

library(tibble)
enframe(regions, "region_id", "country") |>
  unnest(country)

In base R, name the list, and use stack :

setNames(regions, seq_along(regions)) |> 
  stack()

output

    region_id country
1           1      AO
2           1      BI
3           1      BW
4           1      DJ
5           1      DZ
6           1      ET
7           1      GH
8           1      GM
9           1      KE
10          1      LS
11          1      MA
12          1      MR
13          1      MW
14          1      MZ
15          1      NG
16          1      SL
17          1      SZ
18          1      TN
19          1      TZ
20          1      UG
21          1      ZA
22          1      ZM
23          1      ZR
24          1      ZW
25          2      BD
26          2      CN
27          2      HK
28          2      ID
29          2      IN
30          2      KR
31          2      MU
32          2      MY
33          2      PH
34          2      PK
35          2      SG
36          2      TH
37          2      TW
38          2      VN
39          2      AU
40          2      NZ
41          3      AT
42          3      BA
43          3      BE
44          3      BL
45          3      CH
46          3      CI
47          3      CT
48          3      CY
49          3      CZ
50          3      DE
51          3      DK
52          3      EO
53          3      ES
54          3      EU
55          3      FI
56          3      FR
57          3      GA
58          3      GB
59          3      GG
60          3      GR
61          3      HU
62          3      IC
63          3      IE
64          3      IT
65          3      JR
66          3      KZ
67          3      LN
68          3      LU
69          3      LV
70          3      MK
71          3      MT
72          3      NL
73          3      NO
74          3      PO
75          3      PT
76          3      RM
77          3      RS
78          3      RU
79          3      SE
80          3      SJ
81          3      SX
82          3      TR
83          3      UR
84          4      AD
85          4      AE
86          4      BH
87          4      DU
88          4      EG
89          4      IQ
90          4      IR
91          4      IS
92          4      JO
93          4      KW
94          4      LB
95          4      OM
96          4      PS
97          4      QA
98          4      SA
99          4      SY
100         4      YE
101         5      CA
102         5      KY
103         5      US
104         6      AR
105         6      BR
106         6      CB
107         6      CL
108         6      EC
109         6      MX
110         6      PA
111         6      PE
112         6      PY
113         6      UY
114         6      VE
115         7      JP