title: Exchange two elements of a vector in one call
body: <p>I have a vector <code>c(9,6,3,4,2,1,5,7,8)</code>, and I want to switch the elements at index 2 and at index 5 in the vector. However, I don't want to have to create a temporary variable and would like to make the switch in one call. How would I do that?</p>