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index.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>朴素贝叶斯</title>
</head>
<body>
<script>
var StatisticalDesc = function(arr , num){
var newArr = new Array;
for(var i in arr){
newArr[i] = arr[i]
}
var arrLen = newArr.length;
var total = 0,
mean = 0, //均值
variance = 0, //方差
sd = 0, // 标准差
mode = 0, //众数
median = 0; //中位数
// 计算均值
for(var i in newArr ){
total += newArr[i]
}
mean = total / arrLen;
/*
计算方差
注意估计方差的方法
http://baike.baidu.com/item/%E6%96%B9%E5%B7%AE
*/
for(var i in newArr){
variance += (newArr[i]-mean)*(newArr[i]-mean)
}
/*
关于除以n还是除以n-1
如是总体（即估算总体方差），根号内除以n
如是抽样（即估算样本方差），根号内除以（n-1）
*/
variance = variance.toFixed(6) / (arrLen-1)
// 计算标准差
sd = Math.sqrt(variance)
// 计算中位数
newArr.sort(function(a,b){
return a-b
})
if(arrLen % 2 == 0){
median = (newArr[arrLen/2] + newArr[arrLen/2-1]) / 2;
}else{
median = newArr[Math.floor(arrLen/2)]
}
// 计算众数
var maxTimes = 0;
for(var i in newArr){
var temp = this.calcRepeat(newArr,newArr[i]);
if(maxTimes < temp){
maxTimes = temp;
mode = newArr[i];
}
}
if(maxTimes == 1){
mode = 'none'
}
// 保留小数位
if(num) {
sd = sd.toFixed(num)
mean = mean.toFixed(num)
variance = variance.toFixed(num)
};
return {mean:mean,variance : variance , sd:sd , median:median, mode:mode};
}
StatisticalDesc.prototype.calcRepeat = function(arr , value){
var times = 0;
for(var i in arr ){
if(arr[i] == value){
times ++
}
}
return times;
}
var Bayes = function(data,obj){
this.data = data;
this.maleArr = [];
this.femaleArr = [];
this.obj = obj;
this.type_1 = this.data[0].type;
this.type_2 = '';
}
Bayes.prototype.init = function(){
this.class();
var p_male = this.calcP(this.maleArr)
var p_female = this.calcP(this.femaleArr)
if(p_male > p_female){
console.log('猜测为'+this.type_1,parseInt(p_male/p_female))
return '猜测为'+this.type_1+' 概率倍数：' + parseInt(p_male/p_female)
}else{
console.log('猜测为'+this.type_2,parseInt(p_female/p_male))
return '猜测为'+ this.type_2 +' 概率倍数：' + parseInt(p_female/p_male)
}
}
// 把数据先分类
Bayes.prototype.class = function(){
for(var i in this.data){
if(this.data[i].type == this.type_1){
this.maleArr.push( this.data[i] )
}else{
this.femaleArr.push( this.data[i] )
this.type_2 = this.data[i].type
}
}
}
// 计算每部分的概率（正态分布）
Bayes.prototype.norDis = function( x , mean , variance){
var deno = Math.sqrt(2 * Math.PI * variance );
var exp = -(x-mean)*(x-mean)/(2* variance )
return Math.pow(Math.E , exp)/deno
}
// 计算总的概率
Bayes.prototype.calcP = function(arr,obj){
var allArr = [];
for(var i in arr[0]){
if( i != 'type'){
allArr[i] = [];
}
}
for(var i in arr){
for(k in arr[0]){
if( k != 'type'){
allArr[k].push(arr[i][k])
}
}
}
var p_temp = 1;
for(var i in allArr){
var temp_statDesc = new StatisticalDesc(allArr[i] , 3);
p_temp *= this.norDis(this.obj[i],temp_statDesc.mean,temp_statDesc.variance)
}
var p_type = arr.length / this.data.length
var p_guess = p_temp * p_type
return p_guess;
}
window.onload = function(){
var data = [
{type:'男',height:6 , weight:180 , foot: 12 },
{type:'男',height:5.92 , weight:190 , foot: 11 },
{type:'男',height:5.58 , weight:170 , foot: 12 },
{type:'男',height:5.92 , weight:165 , foot: 10 },
{type:'女',height:5 , weight:100 , foot: 6 },
{type:'女',height:5.5 , weight:150 , foot: 8 },
{type:'女',height:5.42 , weight:130 , foot: 7 },
{type:'女',height:5.75 , weight:150 , foot: 9},
]
var bayes = new Bayes(data,{height:6,weight:130,foot:8})
document.write(bayes.init())
}
</script>
</body>
</html>