00 Introduction

Machine Learning definition

Arthur Samuel(1959). Machine Learning: Field of study that gives computers the ability to learn without being explicitly programmed.
Tom Mitchell(1998). A computer program is said to learn from experience E(experience) with respect to some task T(task) and some performance measure P, if its performance on T, as measured by P(probability), improves with experience E.

Machine learning algorithms:

Supervised learning

Regression Problem
Classification Problem

Unsupervised learning

cluster
- Organize computing clusters
- Social network analysis
- Market segmentation
- Astronomical data analysis
Cocktail party problem: find structure in a chaotic environment
```
[W, s, v] = svd((repmat(sum(x.*x, 1), size(x, 1), 1).*x)*x’);
```
Svd 奇异值分解(解线性方程)

Reinforcement learning

recommender systems

Matrices and vectors

definition

(mathbb{R}) refers to the set of scalar real numbers.
(mathbb{R^n}) refers to the set of n-dimemsional vectors of real numbers.

Matlab

更改Octave命令提示
```
PS1(‘>> ’);
```

打印结果

disp(sprintf(‘2 decimals: %0.2f’, a));

特殊矩阵

    ones(a, b);
    rand(a, b);

    randn(a, b);

    eye(a, b);

    magic(a);

绘图

    hold on； %继续绘制
    ploy(x, y); %折线图

    hist(w, h); %条状图

    xlabel(‘’);

    ylabel(‘’);

    title(‘’);

    legend(‘sin’, ‘cos’); %标记曲线

    print -dpng ‘myPlot.png’; %图像存储为文件

    axis（[x_min x_max y_min y_max]）; %缩放

    clf； %清除图像

    imagesc(A) %将矩阵绘制为图像

控制语句

    for i = 1:10
        v(i) = i^2;

    end;

    while i <= 5

        v(i) = 100;

        i = i + 1;

    end;

    if v(1) == 1,

        disp(‘value is one’);

    elseif v(1) == 2,

        disp(‘two’);

    end;

Max

    [value, index] = max()
    max(A, [], 1); %每列最大值

    max(A, [], 2); %每行最大值

函数定义

    function [y1, y2] = squareAndCUbeThisNumber(x)
        y1 = x^2;

        y2 = x^3;

其他命令

命令格式	用途
pwd	打印当前路径
cd	更改路径
ls	列出当前路径的文件
load featuresX.dat	加载数据
load(‘featuresX.dat’)	加载数据
who	显示当前变量列表
whos	详细查看当前变量列表
clear	清空当前变量列表
save xxx.mat	将当前变量列表存储到文件
save xxx.mat -v name	将workspace中的变量[name]存储到文件
save xxx -ascii	以文本形式存储
addpath(‘’)	增加路径
search path()	搜索路径

Experience

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