Regularization

overfitting

如果特征过多，但是训练集不够时，很有可能会出现overfitting

解决overfitting的几种方法

减少特征数

• 手动选择需要保留哪些特征
• Model selection algorithm

Regularization

cosf function

• Keep all the features,but reduce magnitude/values of parameters
  it works well when we have a lot of features,each of which contributes a bit to predicting y