学习大数据第三天：最小二乘法的MATLAB实现

1.点乘:对应元素相乘

A =

1 2

3 4

>> A2=A*A

A2 =

7 10

15 22

>> A2=A.*A

A2 =

1 4

9 16

2.polyfit(x,y,n)：分别为自变量、因变量、最高位数

>> x=0:0.3:3

x =

Columns 1 through 7

0 0.3000 0.6000 0.9000 1.2000 1.5000 1.8000

Columns 8 through 11

2.1000 2.4000 2.7000 3.0000

>> y=4+x.^3+3*x.^2+2

y =

Columns 1 through 7

6.0000 6.2970 7.2960 9.1590 12.0480 16.1250 21.5520

Columns 8 through 11

28.4910 37.1040 47.5530 60.0000

>> y1=polyfit(x,y,3)

y1 =

1.0000 3.0000 0.0000 6.0000

3.另外一个例子：



>> x=[0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1.0]

x =

Columns 1 through 7

0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

Columns 8 through 10

0.8000 0.9000 1.0000

>> y=[2.3201,2.6470,2.9070,3.2885,3.6008,3.9090,4.2147,4.5191,4.8232,5.1275]

y =

Columns 1 through 7

2.3201 2.6470 2.9070 3.2885 3.6008 3.9090 4.2147

Columns 8 through 10

4.5191 4.8232 5.1275

>> p=polyfit(x,y,1)

p =

3.1301 2.0141

>>