http://www.cnblogs.com/wkslearner/p/8933685.html(机器学习中特征的处理及选择)
https://baijiahao.baidu.com/s?id=1593022777941849057&wfr=spider&for=pc(新手必看的十种机器学习算法)
https://bbs.pinggu.org/thread-6289960-1-1.html?t=1523071428484
