tessl/npm-simple-statistics

A JavaScript implementation of descriptive, regression, and inference statistics

—

Pending

Overview

Eval results

Files

Combinatorics

Name: tessl/npm-simple-statistics
Author: tessl

Functions for calculating combinations and permutations of datasets.

Core Imports

import { 
  combinations, 
  combinationsReplacement, 
  permutationsHeap 
} from "simple-statistics";

Capabilities

Combinations

combinations

/**
 * Generates all combinations of k elements from an array
 * @param x - Array of elements to choose from
 * @param k - Number of elements to choose
 * @returns Array of all possible combinations
 */
function combinations<T>(x: T[], k: number): T[][];

Usage Example:

import { combinations } from "simple-statistics";

const letters = ['A', 'B', 'C', 'D'];
const pairs = combinations(letters, 2);
// [['A', 'B'], ['A', 'C'], ['A', 'D'], ['B', 'C'], ['B', 'D'], ['C', 'D']]

const numbers = [1, 2, 3];
const singles = combinations(numbers, 1);
// [[1], [2], [3]]

combinationsReplacement

/**
 * Generates all combinations with replacement of k elements from an array
 * @param x - Array of elements to choose from
 * @param k - Number of elements to choose
 * @returns Array of all possible combinations with replacement
 */
function combinationsReplacement<T>(x: T[], k: number): T[][];

Usage Example:

import { combinationsReplacement } from "simple-statistics";

const dice = [1, 2, 3];
const rollTwice = combinationsReplacement(dice, 2);
// [[1, 1], [1, 2], [1, 3], [2, 2], [2, 3], [3, 3]]

Permutations

permutationsHeap

/**
 * Generates all permutations of an array using Heap's algorithm
 * @param x - Array of elements to permute
 * @returns Array of all possible permutations
 */
function permutationsHeap<T>(x: T[]): T[][];

Usage Example:

import { permutationsHeap } from "simple-statistics";

const colors = ['red', 'green', 'blue'];
const arrangements = permutationsHeap(colors);
// [
//   ['red', 'green', 'blue'],
//   ['green', 'red', 'blue'],
//   ['blue', 'red', 'green'],
//   ['red', 'blue', 'green'],
//   ['green', 'blue', 'red'],
//   ['blue', 'green', 'red']
// ]

// Small example
const abc = ['A', 'B'];
const perms = permutationsHeap(abc);
// [['A', 'B'], ['B', 'A']]

Mathematical Background

Combinations calculate the number of ways to choose k items from n items where order doesn't matter: C(n,k) = n! / (k!(n-k)!)

Combinations with Replacement allow the same item to be chosen multiple times: C(n+k-1,k)

Permutations calculate arrangements where order matters: P(n,k) = n! / (n-k)!

The permutationsHeap function implements Heap's algorithm, which generates all permutations with minimal changes between consecutive permutations, making it efficient for large datasets.

Install with Tessl CLI