Function mode 

pub fn mode(arr: &mut Array) -> Result<Dynamic, Box<EvalAltResult>>

Returns the mode of a 1-D array.

let data = [1, 2, 2, 2, 2, 3];
let m = mode(data);
assert_eq(m, 2);

let data = [1.0, 2.0, 2.0, 2.0, 2.0, 3.0];
let m = mode(data);
assert_eq(m, 2.0);