相關係數

app

var JOURNAL = require('./journal');

//陣列的 indexOf(name) 回傳索引或 -1（不存在）
//這個 hasEvent 用來檢測某事件是否存在
function hasEvent(event, entry) {
	return entry.events.indexOf(event) != -1;
}
//將某事件與變松鼠的關係寫成 [n00, n01, n10, n11] 陣列
function tableFor(event, journal) {
	var table = [0, 0, 0, 0];
	for (var i = 0; i < journal.length; i++) {
		var entry = journal[i], index = 0;
		if (hasEvent(event, entry)) {
			index += 1;
		}
		if (entry.squirrel) {
			index += 2;
		}
		table[index] += 1;
	}
	return table;
}
//根據資料陣列計算出相關係數
function phi(table) {
	return (table[3] * table[0] - table[2] * table[1]) /
		Math.sqrt((table[2] + table[3]) *
							(table[0] + table[1]) *
							(table[1] + table[3]) *
							(table[0] + table[2]));
}
//製作「事件：相關係數」的計算結果物件 phis
function gatherCorrelations(journal) {
	var phis = {};
	for (var entry = 0; entry < journal.length; entry++) {
		var events = journal[entry].events;
		for (var i = 0; i < events.length; i++) {
			var event = events[i];
			if (!(event in phis)) {
				phis[event] = phi(tableFor(event, journal));
			}
		}
	}
	return phis;
}

// var correlations = gatherCorrelations(JOURNAL);
// for (var key in correlations) {
// 	console.log(key + ": " + correlations[key]);
// }

//接下來是先用人眼觀察資料，發現吃花生(0.59)與沒刷牙(-0.38)
//然後將這兩個事件組合成單一事件，再計算其相關係數
//得出絕對正相關（1）的結果
for (var i = 0; i < JOURNAL.length; i++) {
	var entry = JOURNAL[i];
	if (hasEvent("peanuts", entry) && !hasEvent("brushed teeth", entry)) {
		entry.events.push("peanut teeth");
	}
}
console.log(phi(tableFor("peanut teeth", JOURNAL)));

//如果這個程式要改成自動探測，該怎麼做？

data

var JOURNAL = [
  {"events":["carrot","exercise","weekend"],"squirrel":false},
  {"events":["bread","pudding","brushed teeth","weekend","touched tree"],"squirrel":false},
  {"events":["carrot","nachos","brushed teeth","cycling","weekend"],"squirrel":false},
  {"events":["brussel sprouts","ice cream","brushed teeth","computer","weekend"],"squirrel":false},
  {"events":["potatoes","candy","brushed teeth","exercise","weekend","dentist"],"squirrel":false},
  {"events":["brussel sprouts","pudding","brushed teeth","running","weekend"],"squirrel":false},
  {"events":["pizza","brushed teeth","computer","work","touched tree"],"squirrel":false},
  {"events":["bread","beer","brushed teeth","cycling","work"],"squirrel":false},
  {"events":["cauliflower","brushed teeth","work"],"squirrel":false},
  {"events":["pizza","brushed teeth","cycling","work"],"squirrel":false},
  {"events":["lasagna","nachos","brushed teeth","work"],"squirrel":false},
  {"events":["brushed teeth","weekend","touched tree"],"squirrel":false},
  {"events":["lettuce","brushed teeth","television","weekend"],"squirrel":false},
  {"events":["spaghetti","brushed teeth","work"],"squirrel":false},
  {"events":["brushed teeth","computer","work"],"squirrel":false},
  {"events":["lettuce","nachos","brushed teeth","work"],"squirrel":false},
  {"events":["carrot","brushed teeth","running","work"],"squirrel":false},
  {"events":["brushed teeth","work"],"squirrel":false},
  {"events":["cauliflower","reading","weekend"],"squirrel":false},
  {"events":["bread","brushed teeth","weekend"],"squirrel":false},
  {"events":["lasagna","brushed teeth","exercise","work"],"squirrel":false},
  {"events":["spaghetti","brushed teeth","reading","work"],"squirrel":false},
  {"events":["carrot","ice cream","brushed teeth","television","work"],"squirrel":false},
  {"events":["spaghetti","nachos","work"],"squirrel":false},
  {"events":["cauliflower","ice cream","brushed teeth","cycling","work"],"squirrel":false},
  {"events":["spaghetti","peanuts","computer","weekend"],"squirrel":true},
  {"events":["potatoes","ice cream","brushed teeth","computer","weekend"],"squirrel":false},
  {"events":["potatoes","ice cream","brushed teeth","work"],"squirrel":false},
  {"events":["peanuts","brushed teeth","running","work"],"squirrel":false},
  {"events":["potatoes","exercise","work"],"squirrel":false},
  {"events":["pizza","ice cream","computer","work"],"squirrel":false},
  {"events":["lasagna","ice cream","work"],"squirrel":false},
  {"events":["cauliflower","candy","reading","weekend"],"squirrel":false},
  {"events":["lasagna","nachos","brushed teeth","running","weekend"],"squirrel":false},
  {"events":["potatoes","brushed teeth","work"],"squirrel":false},
  {"events":["carrot","work"],"squirrel":false},
  {"events":["pizza","beer","work","dentist"],"squirrel":false},
  {"events":["lasagna","pudding","cycling","work"],"squirrel":false},
  {"events":["spaghetti","brushed teeth","reading","work"],"squirrel":false},
  {"events":["spaghetti","pudding","television","weekend"],"squirrel":false},
  {"events":["bread","brushed teeth","exercise","weekend"],"squirrel":false},
  {"events":["lasagna","peanuts","work"],"squirrel":true},
  {"events":["pizza","work"],"squirrel":false},
  {"events":["potatoes","exercise","work"],"squirrel":false},
  {"events":["brushed teeth","exercise","work"],"squirrel":false},
  {"events":["spaghetti","brushed teeth","television","work"],"squirrel":false},
  {"events":["pizza","cycling","weekend"],"squirrel":false},
  {"events":["carrot","brushed teeth","weekend"],"squirrel":false},
  {"events":["carrot","beer","brushed teeth","work"],"squirrel":false},
  {"events":["pizza","peanuts","candy","work"],"squirrel":true},
  {"events":["carrot","peanuts","brushed teeth","reading","work"],"squirrel":false},
  {"events":["potatoes","peanuts","brushed teeth","work"],"squirrel":false},
  {"events":["carrot","nachos","brushed teeth","exercise","work"],"squirrel":false},
  {"events":["pizza","peanuts","brushed teeth","television","weekend"],"squirrel":false},
  {"events":["lasagna","brushed teeth","cycling","weekend"],"squirrel":false},
  {"events":["cauliflower","peanuts","brushed teeth","computer","work","touched tree"],"squirrel":false},
  {"events":["lettuce","brushed teeth","television","work"],"squirrel":false},
  {"events":["potatoes","brushed teeth","computer","work"],"squirrel":false},
  {"events":["bread","candy","work"],"squirrel":false},
  {"events":["potatoes","nachos","work"],"squirrel":false},
  {"events":["carrot","pudding","brushed teeth","weekend"],"squirrel":false},
  {"events":["carrot","brushed teeth","exercise","weekend","touched tree"],"squirrel":false},
  {"events":["brussel sprouts","running","work"],"squirrel":false},
  {"events":["brushed teeth","work"],"squirrel":false},
  {"events":["lettuce","brushed teeth","running","work"],"squirrel":false},
  {"events":["candy","brushed teeth","work"],"squirrel":false},
  {"events":["brussel sprouts","brushed teeth","computer","work"],"squirrel":false},
  {"events":["bread","brushed teeth","weekend"],"squirrel":false},
  {"events":["cauliflower","brushed teeth","weekend"],"squirrel":false},
  {"events":["spaghetti","candy","television","work","touched tree"],"squirrel":false},
  {"events":["carrot","pudding","brushed teeth","work"],"squirrel":false},
  {"events":["lettuce","brushed teeth","work"],"squirrel":false},
  {"events":["carrot","ice cream","brushed teeth","cycling","work"],"squirrel":false},
  {"events":["pizza","brushed teeth","work"],"squirrel":false},
  {"events":["spaghetti","peanuts","exercise","weekend"],"squirrel":true},
  {"events":["bread","beer","computer","weekend","touched tree"],"squirrel":false},
  {"events":["brushed teeth","running","work"],"squirrel":false},
  {"events":["lettuce","peanuts","brushed teeth","work","touched tree"],"squirrel":false},
  {"events":["lasagna","brushed teeth","television","work"],"squirrel":false},
  {"events":["cauliflower","brushed teeth","running","work"],"squirrel":false},
  {"events":["carrot","brushed teeth","running","work"],"squirrel":false},
  {"events":["carrot","reading","weekend"],"squirrel":false},
  {"events":["carrot","peanuts","reading","weekend"],"squirrel":true},
  {"events":["potatoes","brushed teeth","running","work"],"squirrel":false},
  {"events":["lasagna","ice cream","work","touched tree"],"squirrel":false},
  {"events":["cauliflower","peanuts","brushed teeth","cycling","work"],"squirrel":false},
  {"events":["pizza","brushed teeth","running","work"],"squirrel":false},
  {"events":["lettuce","brushed teeth","work"],"squirrel":false},
  {"events":["bread","brushed teeth","television","weekend"],"squirrel":false},
  {"events":["cauliflower","peanuts","brushed teeth","weekend"],"squirrel":false}
];

// This makes sure the data is exported in node.js —
// `require('./path/to/04_data.js')` will get you the array.
if (typeof module != "undefined" && module.exports)
  module.exports = JOURNAL;