How to find the unique combinations of a string vector elements with a fixed size in R?

A unique combination of vector elements can be found by using combn function with unique function and size argument will help us to identify the size of each of combination. For example, if we have a vector containing string values defined as x then the unique combinations of vector elements of size 2 can be created by using combn(unique(x),2).

Example1

x1<−c("A","B","C","A","D","E","A","C")
combn(unique(x1),2)

Output

[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] "A" "A" "A" "A" "B" "B" "B" "C" "C" "D"
[2,] "B" "C" "D" "E" "C" "D" "E" "D" "E" "E"

Example

combn(unique(x1),3)

Output

[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] "A" "A" "A" "A" "A" "A" "B" "B" "B" "C"
[2,] "B" "B" "B" "C" "C" "D" "C" "C" "D" "D"
[3,] "C" "D" "E" "D" "E" "E" "D" "E" "E" "E"

Example

combn(unique(x1),4)

Output

[,1] [,2] [,3] [,4] [,5]
[1,] "A" "A" "A" "A" "B"
[2,] "B" "B" "B" "C" "C"
[3,] "C" "C" "D" "D" "D"
[4,] "D" "E" "E" "E" "E"

Example

combn(unique(x1),5)

Output

    [,1]
[1,] "A"
[2,] "B"
[3,] "C"
[4,] "D"
[5,] "E"

Example2

x2<−c("India","Russia","India","USA","USA","UK","Egypt","UK")
combn(unique(x2),2)

Output

[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9]
[1,] "India" "India" "India" "India" "Russia" "Russia" "Russia" "USA" "USA"
[2,] "Russia" "USA" "UK" "Egypt" "USA" "UK" "Egypt" "UK" "Egypt"
    [,10]
[1,] "UK"
[2,] "Egypt"

Example

combn(unique(x2),3)

Output

     [,1]     [,2]     [,3]   [,4]     [,5]   [,6]    [,7]     [,8]
[1,] "India" "India" "India" "India" "India" "India" "Russia" "Russia"
[2,] "Russia" "Russia" "Russia" "USA" "USA"   "UK"    "USA"    "USA"
[3,] "USA"    "UK"     "Egypt"  "UK"  "Egypt"  "Egypt" "UK" "Egypt"
      [,9] [,10]
[1,] "Russia" "USA"
[2,] "UK"     "UK"
[3,] "Egypt" "Egypt"

Example

combn(unique(x2),4)

Output

     [,1]  [,2] [,3] [,4] [,5]
[1,] "India" "India" "India" "India" "Russia"
[2,] "Russia" "Russia" "Russia" "USA" "USA"
[3,] "USA" "USA" "UK" "UK" "UK"
[4,] "UK" "Egypt" "Egypt" "Egypt" "Egypt"

Example

combn(unique(x2),5)

Output

      [,1]
[1,] "India"
[2,] "Russia"
[3,] "USA"
[4,] "UK"
[5,] "Egypt"

Example3

x3<−c("G1","G2","G3","G1","G2","G4","G5","G3","G5","G2")
combn(unique(x3),2)

Output

[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] "G1" "G1" "G1" "G1" "G2" "G2" "G2" "G3" "G3" "G4"
[2,] "G2" "G3" "G4" "G5" "G3" "G4" "G5" "G4" "G5" "G5"

Example

combn(unique(x3),3)

Output

[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] "G1" "G1" "G1" "G1" "G1" "G1" "G2" "G2" "G2" "G3"
[2,] "G2" "G2" "G2" "G3" "G3" "G4" "G3" "G3" "G4" "G4"
[3,] "G3" "G4" "G5" "G4" "G5" "G5" "G4" "G5" "G5" "G5"

Example

combn(unique(x3),4)

Output

[,1] [,2] [,3] [,4] [,5]
[1,] "G1" "G1" "G1" "G1" "G2"
[2,] "G2" "G2" "G2" "G3" "G3"
[3,] "G3" "G3" "G4" "G4" "G4"
[4,] "G4" "G5" "G5" "G5" "G5"

Example

combn(unique(x3),5)

Output

     [,1]
[1,] "G1"
[2,] "G2"
[3,] "G3"
[4,] "G4"
[5,] "G5"

Example4

x4<−c("HOT","COLD","SWEET","BITTER","HOT","SWEET")
combn(unique(x4),2)

Output

combn(unique(x4),2)
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] "HOT" "HOT" "HOT" "COLD" "COLD" "SWEET"
[2,] "COLD" "SWEET" "BITTER" "SWEET" "BITTER" "BITTER"

Example

combn(unique(x4),3)

Output

[,1] [,2] [,3] [,4]
[1,] "HOT" "HOT" "HOT" "COLD"
[2,] "COLD" "COLD" "SWEET" "SWEET"
[3,] "SWEET" "BITTER" "BITTER" "BITTER"

Example

combn(unique(x4),4)

Output

      [,1]
[1,] "HOT"
[2,] "COLD"
[3,] "SWEET"
[4,] "BITTER"