Question

Is there a straightforward way to generate all possible permutations of a vector of integers (1 to max 999) that specifically excludes duplicated elements?

For example, for a vector with three elements in a range of 1 to 9 the sequence 1 2 3 would be acceptable, as would 1 2 9 but 1 2 2 would be invalid. The sequence must contain exactly n elements (in this case, three). EDIT: to avoid confusion, the order is significant, so 1 2 9 and 9 2 1 are both valid and required.

There are many questions on permutations and combinations using R on SO (such as this and this) but none that seem to fit this particular case. I’m hoping there’s an obscure base R or package function out there that will take care of it without me having to write a graceless function myself.

Answer 1

Using gtools package:

require(gtools)
permutations(n = 9, r = 3, v = 1:9)
# n -> size of source vector
# r -> size of target vector
# v -> source vector, defaults to 1:n
# repeats.allowed = FALSE (default)