Learning from Imbalanced Classes

https://www.svds.com/learning-imbalanced-classes/

 下采样即 从大类负类中随机取一部分，跟正类（小类）个数相同，优点就是降低了内存大小，速度快！

http://www.tuicool.com/articles/r2ee2ie

Learn more about SMOTE, see the original 2002 paper titled “ SMOTE: Synthetic Minority Over-sampling Technique “.

There are a number of implementations of the SMOTE algorithm, for example:

• In Python, take a look at the “ UnbalancedDataset ” module. It provides a number of implementations of SMOTE as well as various other resampling techniques that you could try.
• In R, the DMwR package provides an implementation of SMOTE.