jStat: JavaScript Statistical Library

Common errors

• TypeError: require(...) is not a function

  cause Attempting to call `require('jstat')` directly as a function in CommonJS.
  fix The `jstat` module exports an object. You need to access its `jStat` property: `const { jStat } = require('jstat');`

• TypeError: Cannot read properties of undefined (reading 'normal')

  cause `jStat` was not correctly imported or accessed, leading to `jStat` being `undefined` or the wrong object when trying to call a method like `normal()`.
  fix Ensure `jStat` is correctly destructured from the module import: `const { jStat } = require('jstat');` for CJS, or `import * as jStatModule from 'jstat'; const jStat = jStatModule.jStat;` for ESM.

• npm ERR! 404 Not Found - GET https://registry.npmjs.org/jStat - Not found

  cause Using the incorrect, case-sensitive package name `jStat` instead of `jstat` during installation.
  fix Install using the correct, all-lowercase package name: `npm install jstat`.

Warnings

• breaking The npm package name changed from the case-sensitive `jStat` to the all-lowercase `jstat`. Installing `jStat` will lead to an outdated or non-existent package.
  Fix: Always use `npm install jstat` (lowercase) for installation.
• gotcha The `jstat` module does not export its main functionality directly. Instead, it exports an object containing `jStat` and `j$` properties. Direct `require('jstat')` or ESM `import jStat from 'jstat'` will result in an object, not the callable function.
  Fix: Access the `jStat` (or `j$`) property from the imported module object, e.g., `const { jStat } = require('jstat');` for CommonJS or `import * as jStatModule from 'jstat'; const jStat = jStatModule.jStat;` for ESM.
• gotcha The library appears to be largely unmaintained. The last release was over four years ago, and there has been no significant activity on its GitHub repository. This suggests potential risks for security patches, bug fixes, or compatibility with newer JavaScript environments.
  Fix: Evaluate alternatives if active maintenance, modern features, or ongoing support are critical for your project. Be prepared to fork or maintain it yourself if necessary.
• gotcha When used in a browser via a script tag, `jStat` pollutes the global `window` object by adding `window.jStat` and `window.j$`. This can lead to naming conflicts in environments with many global scripts.
  Fix: Consider using a module bundler (like Webpack or Rollup) to encapsulate the library, or rename the global variable immediately after loading if conflicts are expected.

Install

• npm install jstat npm
• yarn add jstat yarn
• pnpm add jstat pnpm

Imports

• jStat
  wrong:

  const jStat = require('jstat');

  correct:

  const { jStat } = require('jstat');

  The `jstat` module exports an object containing `jStat` and `j$` properties. Destructure or access them explicitly in CommonJS.
• jStat
  wrong:

  import { jStat } from 'jstat';

  correct:

  // <script src='path/to/jstat.min.js'></script>
  const jstat = window.jStat;

  When loaded via a script tag in a browser, `jStat` becomes a global property on the `window` object.
• jStat
  wrong:

  import jStat from 'jstat';

  correct:

  import * as jStatModule from 'jstat';
  const jStat = jStatModule.jStat;

• j$

  const { j$ } = require('jstat');

  An alias for `jStat`, also exported from the module object for CommonJS.

Quickstart

Demonstrates importing jStat, calculating basic statistics (mean, standard deviation) from a dataset, using a normal distribution's CDF, and generating a random sample.

import * as jStatModule from 'jstat';
const jStat = jStatModule.jStat;

// Define a dataset
const dataset = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

// Calculate mean and standard deviation
const mean = jStat(dataset).mean();
const stdev = jStat(dataset).stdev();

console.log(`Dataset: [${dataset.join(', ')}]`);
console.log(`Mean: ${mean}`);
console.log(`Standard Deviation: ${stdev}`);

// Example of using a distribution function: Normal CDF
const normalDist = jStat.normal(mean, stdev);
const cdfAt7 = normalDist.cdf(7);
console.log(`CDF at x=7 for Normal(${mean.toFixed(2)}, ${stdev.toFixed(2)}): ${cdfAt7.toFixed(4)}`);

// Example of generating a sample
const sample = normalDist.sample(5);
console.log(`Random sample of 5 from Normal(${mean.toFixed(2)}, ${stdev.toFixed(2)}): [${sample.map(s => s.toFixed(2)).join(', ')}]`);