ml-distance/src/similarities/kumarHassebrook.ts

Distance and similarity functions to compare vectors

import { NumberArray } from 'cheminfo-types';
/**
 *Returns Kumar-Hassebrook similarity between vectors a and b
 * @link [Kumar-Hassebrook Similarity algorithm](https://www.naun.org/main/NAUN/ijmmas/mmmas-49.pdf)
 * @param a - first vector
 * @param b - second vector
 *
 */
export default function kumarHassebrook(
  a: NumberArray,
  b: NumberArray,
): number {
  let p = 0;
  let p2 = 0;
  let q2 = 0;
  for (let i = 0; i < a.length; i++) {
    p += a[i] * b[i];
    p2 += a[i] * a[i];
    q2 += b[i] * b[i];
  }
  return p / (p2 + q2 - p);
}