[ 机器学习 - 吴恩达 ] | 1-2 What is machine learning

Machine learning definition

• Arthur Samuel (1959). Machine Learning: Field of study that gives computers the ability to learn without being explicitly (明确地) programmed. (在没有明确地设置下，使计算机具有学习能力的研究领域)
• Tom Michell (1998). Well-posed (适当的) Learning Problem: A computer program is said to learn from experience E with respect to some task T and some performance measure P, if its performance on T, as measured by P, improves with experience E. (一个适当的学习问题：计算机程序从经验E中学习，解决某一任务T，进行某一性能度量P，通过P测定在T上的表现因经验E而提高。)

Machine learing algorithms:

• Supervised learning

• Unsupervised learning

Others: Reinforcement learning, recommender systems.

Also talk about: Practical advice for applying learning algorithms.

Q-1: Suppose your email program watches which emils you do or do not mark as spam, and based on that learns how to better how to better filter spam. What is the task T in this setting?
Answer: A
? A: Classifying emails as spam or not spam.
? B: Watching you label emails as spam or not spam. -> E
? C: The number (or fraction (分数)) of emails correctly classified as spam/not spam. -> P
? D: None of the above - this is not a machine learning problem.