count ties after rank?
On Nov 21, 2011, at 2:50 PM, Peter Langfelder wrote:
On Mon, Nov 21, 2011 at 11:36 AM, Hao, Zhaozhe <haozhaozhe at ou.edu> wrote:
Hello! I need to use Kruskal-Wallis test and post-hoc test (Dunn's test) for my data. But when I searched around, I only found this function: kruskal.test. But nothing for Dunn's test. So I started to write one myself. But I do not know how to count ties in the data frame. I can use for loops but it seems long and unnecessary since the rank function actually knows the ties. So can anyone give me a hint on how I can "count" the number of ties?
If you just need the overall number of ties in a vector (say x), you can get it by nTies = length(x) - length(unique(x))
And if you wnat to know which ties are which you can do: table(x)[table(x) > 1]
This will not work if missing data are present, so you will have to remove those first.
table() would ignore missing data (assuming it were properly NA not- valued). > x <- sample(c(1:10,NA,NA), 20, replace=TRUE) > table(x)[table(x) >1] x 1 4 7 9 10 2 3 2 2 2 > x [1] 7 10 3 9 NA NA 2 4 10 NA NA 4 5 9 6 4 1 1 7 8
David Winsemius, MD West Hartford, CT