Andrew Ng的课程：

Week 1:

  • Welcome: Machine Learning的简单介绍：包括Database mining （Web click data, medical records）, Applications can't programmed by hand.

  • What is machine learning: Tom Mitchell(1998): A computer program is said to learn from experience E with respect to some task T and some performance P, if its performance on T, as measured by P, improves with experience E.
    • 　　In general, any machine learning problem can be assigned to one of two broad classifications: Supervised learning and Unsupervised learning.

  • 　Supervised learning: 　 regression problem (continuous value) and classification problem (discrete value).

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  • Unsupervised learning:　　

  • Model representation:  

    • usually m is denoted as number of trainning examples.
    • 所谓model不过是建立模型，给出prediction,然后反馈，校准model.这就是监督学习的过程。但实际上无监督的本质不也是这样吗？其实抛开所谓机器学习，任何学习的本质都是这样。
  • Cost function:　　

     

    • 　　mathematics always show us the simplest idea.
  • Cost function--Intuition I: 　　h is a function of x and J is a function of theta.
  • Cost function-- Intuition II: 介绍了contour plot。

  • Gradient Descent: 　

  •  Gradient Descent Intuition I: 

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    Gradient descent for linear regression: