How does ties.method argument of R's rank function work?

Question

I am using rank(a, ties.method="max") to rank a. But I am not quite sure what does ties.method="max" do. Can you please help?

Answer 1

Ties.method specifies the method rank uses to break ties. Suppose you have a vector c(1,2,3,3,4,5). It's obvious that 1 is first, and 2 is second. However, it's not clear what ranks should be assigned to the first and second 3s. Ties.method determines how this is done. There are a few options:

• average assigns each tied element the "average" rank. The ranks would therefore be 1, 2, 3.5, 3.5, 5, 6

• first lets the "earlier" entry "win", so the ranks are in numerical order (1,2,3,4,5,6)

• min assigns every tied element to the lowest rank, so you get 1,2,3,3,5,6

• max does the opposite: tied elements get the highest rank (1,2,4,4,5,6)

• random breaks ties randomly, so you'd get either (1,2,3,4,5,6) or (1,2,4,3,5,6).