Permutations in R

Question

how can R generate permutations as follows:

• numbers to be used are 1, 2, 5 and 10
• combination should be based on 2 numbers
• order of the combinations is not important

for the above, this results in:

1- 1, 2
2- 1, 5
3- 1, 10
4- 2, 5 
5- 2, 10
6- 5, 10

Answer 1

Use combn :

combn(c(1,2,5,10),2) # before the comma is your values to be used, after is the number of elements to be chosen
     [,1] [,2] [,3] [,4] [,5] [,6]
[1,]    1    1    1    2    2    5
[2,]    2    5   10    5   10   10