Function maxk 

pub fn maxk(arr: &mut Array, k: INT) -> Result<Array, Box<EvalAltResult>>

Returns the k highest values from an array. Fails if the input is not an array, or if it is an array with elements other than INT or FLOAT.

let data = [32, 15, -7, 10, 1000, 41, 42];
let mk = maxk(data, 3);
assert_eq(mk, [41, 42, 1000]);

let data = [32, 15, -7.0, 10, 1000, 41.0, 42];
let mk = maxk(data, 3);
assert_eq(mk, [41.0, 42.0, 1000.0]);