一、什么是机器学习？
已有的数据(经验)，训练某种模型，利用此模型预测未来。
1998年Tom Mitchell对机器学习给出了一个更加正式的定义：A computer program is said to learn from experience E with respect to some task T and some performance measure P,if its performance on T,as measured by P,improves with experience E.
1998年Tom
