Function rstats::vecvecg::occurs

pub fn occurs<T>(sasc: &[T], sdesc: &[T], val: T) -> usize where
    T: PartialOrd<T> + Copy + Display, 

Counts occurrences of val, using previously obtained ascending explicit sort sasc and descending sort sdesc. This is to facilitate counting of many different values without ever having to repeat the sorting. This function is very efficient at counting numerous repetitions in large sets (e.g. probabilities in stats). Binary search from both ends is deployed: O(2log(n)).

Example:

use crate::indxvec::Indices;
use indxvec::merge::{sortidx,occurs};
let s = [3.141,3.14159,3.14159,3.142];
let sindx = sortidx(&s); // only one sort ever
let sasc = sindx.unindex(&s,true);
let sdesc = sindx.unindex(&s,false);
assert_eq!(occurs(&sasc,&sdesc,3.14159),2);