data.tableを展開して、グループ化されたプリンシパルとエイリアスの組み合わせを作成します

私は以下を持っていますdata.table：

require(data.table)
dt = data.table(structure(list(postcode = c("4101", "4101", "4101", "4101", "4101", 
"4101", "4101", "4101", "4272", "4272", "4272", "4272", "4272"
), suburb = c("SOUTH BRISBANE", "HIGHGATE HILL", "WEST END", 
"WOOLLOONGABBA", "DUTTON PARK", "HIGHGATE HILL", "SOUTH BRISBANE", 
"WEST END", "BENOBBLE", "EAGLE HEIGHTS", "NORTH TAMBORINE", "MOUNT TAMBORINE", 
"TAMBORINE MOUNTAIN"), type = c("A", "A", "A", "A", "A", "P", 
"P", "P", "A", "A", "A", "A", "P")), class = "data.frame", row.names = c(NA, 
-13L)))

 dt
    postcode             suburb type
 1:     4101     SOUTH BRISBANE    A
 2:     4101      HIGHGATE HILL    A
 3:     4101           WEST END    A
 4:     4101      WOOLLOONGABBA    A
 5:     4101        DUTTON PARK    A
 6:     4101      HIGHGATE HILL    P
 7:     4101     SOUTH BRISBANE    P
 8:     4101           WEST END    P
 9:     4272           BENOBBLE    A
10:     4272      EAGLE HEIGHTS    A
11:     4272    NORTH TAMBORINE    A
12:     4272    MOUNT TAMBORINE    A
13:     4272 TAMBORINE MOUNTAIN    P

特定の郵便番号グループに対して、可能なすべてのプリンシパルバリエーションをポストコードグループ内のすべてのエイリアス(type = A)およびプリンシパル(type = P)タイプに割り当てるように拡張する必要があります。

例：最初の郵便番号グループの場合：

dt[postcode == 4101]

   postcode         suburb type
1:     4101 SOUTH BRISBANE    A
2:     4101  HIGHGATE HILL    A
3:     4101       WEST END    A
4:     4101  WOOLLOONGABBA    A
5:     4101    DUTTON PARK    A
6:     4101  HIGHGATE HILL    P
7:     4101 SOUTH BRISBANE    P
8:     4101       WEST END    P

5つのエイリアスタイプ(type = A)と3つのプリンシパルタイプがあります(type = P)。

出力(5 (type=A) * 3 (type=P)) + 3 (type=P)) = 18は行になり、次のようになります。

postcode         suburb type  principal
    4101 SOUTH BRISBANE    A  HIGHGATE HILL
    4101 SOUTH BRISBANE    A  SOUTH BRISBANE
    4101 SOUTH BRISBANE    A  WEST END
    4101  HIGHGATE HILL    A  HIGHGATE HILL
    4101  HIGHGATE HILL    A  SOUTH BRISBANE
    4101  HIGHGATE HILL    A  WEST END
    4101       WEST END    A  HIGHGATE HILL
    4101       WEST END    A  SOUTH BRISBANE
    4101       WEST END    A  WEST END
    4101  WOOLLOONGABBA    A  HIGHGATE HILL
    4101  WOOLLOONGABBA    A  SOUTH BRISBANE
    4101  WOOLLOONGABBA    A  WEST END
    4101    DUTTON PARK    A  HIGHGATE HILL
    4101    DUTTON PARK    A  SOUTH BRISBANE
    4101    DUTTON PARK    A  WEST END
    4101  HIGHGATE HILL    P  HIGHGATE HILL
    4101 SOUTH BRISBANE    P  SOUTH BRISBANE
    4101       WEST END    P  WEST END

これはサンプルデータです。実際には、何千もの郵便番号グループがあります。