CS156 Machine Learning -1 The Learning Problem 筆記

大綱

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example of machine learning

Predicting how a viewer will rate a movie

Movie rating - a solution

spectrum 範圍
The essece of machine learning:編程

  • A pattern exists
  • We cannot pin it down mathematially.
  • We have data on it.

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The learning approah

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Components of learning

Metaphor(比喻): Credit approval
Applicant information:app

kind info
age 23 years
gender male
annual salary $30,000
years in residence 1 year
years in job 1 year
current debt $15,000
... ...

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可認爲這是一個d-維向量
其元素依次是 salary, years in residence, years in job, current debt...
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y在這裏僅表示 extend credit (1) & not to extend credit (-1)
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It is a function from domain X,
X is a set of all input x (the set of vectors of d-dimention), it's a d-dimention Euclidean space(歐氏空間)
y : a binary co-demain
endeavors 盡力
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f is unknown, but g is known, and we credit it
the value of g is supposed to approximates f
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爲何須要hypothesis setdom

  • no downside for including a hypothesis set in the formalization, but there is an upsideide

    • no downside:函數

      • no loss of generality in putting
    • upside:idea

      • the hypothesis set will play a pivotal role in the theory of learning, make the theory go through?

Solution components

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quadratic programming 二次編程???
glorious 最好的,極好的
pinpoint 精確查找spa

A simple model

A simple hypothesis set - the `pereptron'

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x1 salary, x2 years in residence, x3 years in job, x4 current debt ... xd ...
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根據實際狀況,分別給不一樣的權重
視爲credit score
threshold 臨界值
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we start with random weights that will give a random line
notation 符號,記法
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引入 x0 = 1 能夠化簡表達式
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A simple learning algorithm - PLA

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經過這種方法,咱們儘量的使這些點被正確分類
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只要是線性的,當迭代次數足夠多後,總能所有分類正確
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Types of learning

Basic premise of learning

premise 前提
underlying process 基本過程
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Supervised Learning

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vending 販賣

Unsupervised Learning

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雖然沒辦法知道具體類別,可是能夠作出分類

Reinforcement Learning

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a learning puzzle

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