ml-distance/src/similarities/tanimoto.ts

Distance and similarity functions to compare vectors

import { NumberArray } from 'cheminfo-types';
/**
 *Returns the Tanimoto similarity  between vectors p and q, and accepts the bitVector use, see the test case for an example
 * @link [Tanimoto similarity algorithm](https://www.naun.org/main/NAUN/ijmmas/mmmas-49.pdf)
 * @param a - first vector
 * @param b - second vector
 * @param bitvector - bitVector
 *
 */
export default function tanimoto(
  a: NumberArray,
  b: NumberArray,
  bitvector?: boolean,
): number {
  if (bitvector) {
    let inter = 0;
    let union = 0;
    for (let j = 0; j < a.length; j++) {
      inter += a[j] && b[j];
      union += a[j] || b[j];
    }
    if (union === 0) {
      return 1;
    }
    return inter / union;
  } else {
    let p = 0;
    let q = 0;
    let m = 0;
    for (let i = 0; i < a.length; i++) {
      p += a[i];
      q += b[i];
      m += Math.min(a[i], b[i]);
    }
    return 1 - (p + q - 2 * m) / (p + q - m);
  }
}