Lin Xuan Tian cornerstone of machine learning courses Notes 1 - The Learning Problem

Source | AI algorithms and image processing 

main content

  • What is Machine Learning

  • Applications of Machine Learning

  • Components of Machine Learning

  • Machine Learning and Other Fields


What is Machine Learning

What is "learning"? Human learning is through observation, the accumulation of experience, master a skill or ability. Just as we grew up learning to identify letters, recognizing Chinese characters, it is the process of learning. And Machine Learning (Machine Learning), as the name suggests, is to make a machine (computer) can be the same to humans by observing the large amount of data and training, found that the law of things, get some sort of problem analysis, problem-solving skills.

Machine learning process starting from data, calculated after the computer eventually get a certain kind of performance.

For example, through the computer so that the computer learn to predict the stock. Using the data a decade ago to learn, tell me tomorrow that how to invest, if the machine did, then that machine really learned something. It is our hope that machine learning can do.

Example: How to identify a tree

  • A program designed to define a tree, it is very difficult

  • By studying the data to identify a tree (3 years old children can do)

  • Machine learning system designed to identify a tree than a program easier and more

Through our brain to analyze these things more difficult, because you want to learn myself and analyzed by the machine and found that these laws.

Machine learning to build a complex system of time is an optional method:

such as:

  • When humans can not do a complex system, all the laws are written clearly, such as robotic exploration of Mars, no way to predict robot on Mars What will happen, for example, encountered a pit, how to do, which requires its own machine to learn how to deal with

  • No way to define a rule when - voice / visual recognition

  • Some people thought the application - stock market trading

  • In the large-scale data a user oriented issues - individual users market

Machine learning to do, is to teach a computer similar to fishing methods, it can be good enough for a lifetime.

So under what scenario, consider using machine learning to solve it?

Three key conditions Machine Learning:

  • There are some potential things law itself can go to learn, and have clear goals

  • There are some things the rules, but we do not know how to put it down to write the code

  • Machine learning materials needed, otherwise the machine does not know how to learn

When the three key conditions are met before considering the use of machine learning

Test & answers:

1, forecast the next few minutes after the child cry? no (no rules)

2, to determine whether there is a round figure? no (rules can be easily defined)

3, to determine whether the user to distribute the letter with the card? yes, is not easy programming, a large customer history information

4, when the Earth will be destroyed? no (not enough data)

Applications of Machine Learning

Machine learning in all aspects of our basic necessities have applications.

(1)Food:

Source: Twitter (Evaluation positioning +)

Function: How do you know this is unfortunately the taste of food

(2)Clothing

Data: Product images, user outfit

Function: Tell us how to match clothes can be more Fashion

(3)Housing

Data: architectural features of the house, use of energy

Features: the ability to predict the energy saving houses above

(4)Transportation

Data: traffic light images and meanings

Function: to accurately identify traffic light signal

The above are just a few examples, of course, there are many examples like this!

Application of machine learning in education

Data: Some student records online lesson, and answer records and school records

Function: to predict what the student union, what will not, and recommended some information.

Then the machine learning how to design it?

  • Data from 3000 are given nine million students

  • Using machine learning to automatically determine the difficulty of the problem, etc.

Entertainment applications, recommendation system

Data: How many users like what movie

Function: predict how much a user likes a probability not seen the movie

So the computer is to learn how these features do?

Using the model and the user to describe the movie with a bunch of features, find the inner product of two strings feature, if multiplied score high, give a very high recommendation scores. But we have no way to define these characteristics, so the machine learning by past data, to learn these characteristics, and predict the user how much they like the movie.

Test & answers

Machinery used in the following areas which can not?

1, the financial (market forecast)

2, medical (predicted efficacy)

3, legal (automatically gives a summary from public documents, easy to find and read)

Any yes 4, not above

Components of Machine Learning


How to formulate the problem of machine learning

Basic terms:

  • Enter: x (user behavior)

  • Output: y (forecast based on the results of good / bad, decide whether or not to card issuers)

  • The objective function: f, unknown rule ---> objective function

  • Data, training samples (data collected in the past)

  • Hypothesis, the hypothesis choose the best moment of the corresponding function is called g, g that best represents the inherent law of things, we also want to get the final model expression

Machine Learning flow chart:

Data from unknown laws by learning algorithms to dig, so close to the final g f

important point:

  • The objective function, f is unknown

  • Hypothesis is to g as close to f, but may still differ from f

For example, a credit card, for example

g in the end look like

Today decide whether or not to the customer credit card, here are some possible formulas

h1: annual income does not exceed 800,000 more than give

h2: more than 100,000 to the credit card debt

h3: job less than two years to give him the credit card

All possible h, g are put in the collection, and the most likely outcome from the collection found

Model = + learning algorithm hypothesis

Definition of machine learning: starting from data, machine learning algorithms to calculate a hypothesis (hypothesis) g, g we hope this to be very close to what we most desire that f.

Test & answers

Recommended songs

Machine Learning and Other Fields

Machine learning-related fields are:

  • Data Mining (Data Mining) -> dig some useful information from the data

  • AI (Artificial Intelligence) -> calculate and show something very clever behavior (such as AI chess)

  • Statistics (Statistics) -> use data to make some inferences (such as coin issue)

Machine learning and data mining, are very much alike in some places is still the same, inseparable

Machine learning is one way of implementing artificial intelligence

Statistics is one way to achieve machine learning, statistical results are given more attention to the use of mathematical theory, few concerns calculation. Statistical machine learning to provide a lot of useful tools.

Test & answers

to sum up


This lesson introduces the main concepts of machine learning, machine learning is actually a function from the data found, then the function we most desire and goal is to find very close. Machine learning has applications in many places, the core algorithms, data (information), hypothesis (hypothesis) finally got g.

Machine learning and data mining, artificial intelligence, statistical relationship between these three areas to be compared, and in various fields, they each have their own orientation.

References:

https://www.bilibili.com/video/BV1Cx411i7op?p=1

https://blog.csdn.net/red_stone1/article/details/101303228

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