机器学习（介绍）
"A computer program is said to learn from experience E with respect to some class of tasks T and performance measure P, if its performance at tasks in T, as measured by P, improves with experience E."
Example: playing checkers.
E = the experience of playing many games of checkers
T = the task of playing checkers.
P = the probability that the program will win the next game.
机器学习就是从经验E中学习，完成任务T，P是完成效果
监督学习
有标签
1、线性回归
2、分类
无监督学习
无标签
1、盲目分类
模型描述
用训练集通过学习算法，得到一个假设函数，输入x预测y
假设函数：hθ（x）=θ0+θ1x