enhancedmath/lib/Probability/permutation.js

This package contains some enhanced mathematical operations

import factorial from '../factorial';
/**
 * Calculates the probability of a permutation with a population of n and a sample size r
 * @param n The total population
 * @param r The sample size
 */
const permutation = (n, r) => {
    if (0 > r || r > n) {
        return undefined;
    }
    if (!factorial(n) || !factorial(r) || !factorial(n - r)) {
        return undefined;
    }
    return factorial(n) / factorial(n - r);
};
export default permutation;