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Adds standard deviation to IMDb ratings breakdown pages.
// ==UserScript==
// @name IMDb Standard Deviation
// @namespace http://userscripts.org/users/7063
// @include https://www.imdb.com/title/tt*/ratings
// @include https://www.imdb.com/title/tt*/ratings-*
// @include https://www.imdb.com/title/tt*/ratings?*
// @version 2019.1.1.21.17
// @grant none
// @description Adds standard deviation to IMDb ratings breakdown pages.
// ==/UserScript==
/*eslint-env browser*/
"use strict";
(function () {
const main = document.querySelector("#main");
if (main) {
const votes = [...main.querySelector("table").rows].slice(1)
.map(k => +k.cells[2].textContent.replace(/[\s,]/g, ""));
const [product, votecount] = votes.reduce(([p, v], c, i) => [p + c * (10 - i), v + c], [0, 0]);
const sumOfSquares = votes.reduce((p, c, i) => p + Math.pow(10 - i - product / votecount, 2) * c, 0);
main.querySelector("table ~ .allText").textContent += `\xA0 Standard Deviation = ${
Math.sqrt(sumOfSquares / (votecount - 1)).toFixed(2)}`;
}
}());