coursera上吴恩达老师的机器学习课程作业和文档
https://www.coursera.org/learn/machine-learning
https://s3.amazonaws.com/spark-public/ml/exercises/on-demand/machine-learning-ex1.zip
https://s3.amazonaws.com/spark-public/ml/exercises/on-demand/machine-learning-ex2.zip
so on...