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


>>