http://blog.jasonding.top/2015/04/05/Machine%20Learning/%E3%80%90%E8%AE%A1%E7%AE%97%E6%9C%BA%E8%A7%86%E8%A7%89%E3%80%91%E6%8F%90%E5%8F%96%E8%A7%86%E9%A2%91%E4%B8%AD%E7%9A%84%E5%89%8D%E6%99%AF%E7%89%A9%E4%BD%93/
