转载自：http://blog.csdn.net/yechaodechuntian/article/details/37394967
https://www.zhihu.com/question/19645541
http://peghoty.blog.163.com/blog/static/49346409201302595935709/
准确率(Precision)、召回率(Recall)以及F值(F-Measure)
原文：http://www.cnblogs.com/zl0372/p/5701112.html