我试图以应用Bayesian rating formula,但如果我评级1 5000数百名,最终评级是大于5洪水贝叶斯评分创造价值超出范围
例如,一个给定的项目没有投票,经过投票17万次,1星,最终评分为5.23。如果我评价为100,则它具有正常值。
这是我在PHP中的。
<?php
// these values came from DB
$total_votes = 2936; // total of votes for all items
$total_rating = 582.955; // sum of all ratings
$total_items = 202;
// now the specific item, it has no votes yet
$this_num_votes = 0;
$this_score = 0;
$this_rating = 0;
// simulating a lot of votes with 1 star
for ($i=0; $i < 170000; $i++) {
$rating_sent = 1; // the new rating, always 1
$total_votes++; // adding 1 to total
$total_rating = $total_rating+$rating_sent; // adding 1 to total
$avg_num_votes = ($total_votes/$total_items); // Average number of votes in all items
$avg_rating = ($total_rating/$total_items); // Average rating for all items
$this_num_votes = $this_num_votes+1; // Number of votes for this item
$this_score = $this_score+$rating_sent; // Sum of all votes for this item
$this_rating = $this_score/$this_num_votes; // Rating for this item
$bayesian_rating = (($avg_num_votes * $avg_rating) + ($this_num_votes * $this_rating))/($avg_num_votes + $this_num_votes);
}
echo $bayesian_rating;
?>
即使我用1或2泛滥:
$rating_sent = rand(1,2)
最终的评价后10万次投票是在5
我只是做了使用
$rating_sent = rand(1,5)
新的考验
而且在10万之后,我的数值完全超出了范围(10.53)。我知道,在正常情况下,没有项目会获得17万张选票,而其他所有项目都不会获得投票。但是我想知道我的代码是否有问题,或者如果这是考虑到大量投票的贝叶斯公式的预期行为。
编辑
只是为了说清楚,这里是一些变量更好的解释。
$avg_num_votes // SUM(votes given to all items)/COUNT(all items)
$avg_rating // SUM(rating of all items)/COUNT(all items)
$this_num_votes // COUNT(votes given for this item)
$this_score // SUM(rating for this item)
$bayesian_rating // is the formula itself
的公式为:((avg_num_votes * avg_rating) + (this_num_votes * this_rating))/(avg_num_votes + this_num_votes)
。取自here
你用来计算'$ bayesian_rating'变量的值? '$ avg_num_votes'等。 – Ishtar 2011-05-15 21:46:11
我编辑了这个问题,为一些变量添加了更好的解释。我开始认为,当一个项目获得太多票数而其他项目没有得到新票时,这个项目的评级往往是无限的。 – rlcabral 2011-05-15 22:12:52
但是,实际值是什么?你能打印它们吗? – Ishtar 2011-05-15 22:24:49