Swaps the order of the attributes to create a new design candidate. For example, if the attributes in the first and fourth choice situation (row) are swapped, then (1, 2, 1, 3, 2, 3) becomes( 3, 2, 1, 1, 2, 3).
swap(x)A vector of attribute levels
The algorithm randomly samples 2 row positions that are swapped and the swaps are independent across attributes and alternatives
Hensher, D. A., Rose, J. M. & Greene, W., 2005, Applied Choice Analysis, 2nd ed., Cambridge University Press