fivetwo.m

给定数的最小二乘拟合以及在给定两组数据下用矩法估计以及用拟和估计得对比

clc;
clear;
load m5_3.dat;

% 第一问
z=mean(m5_3)
dertapingfang=var(m5_3)


% 第二问
x=log(z/3)


% 第三问
for i=1:100
    w(i)=m5_3(i)-3*exp(x);
end
max(w)
min(w)
buchang=(max(w)-min(w))/12;
a=zeros(1,12);
q=0;
for i=min(w):buchang:(max(w)-buchang)
    q=q+1;
    for j=1:100
        if (w(j)>=i && w(j)<i+buchang)
            a(q)=a(q)+1;
        else
            continue;
        end
    end
end
t=linspace(-6,6,12);
xishu=polyfit(t,a/100,4);
t=-6:0.001:6
plot(t,xishu(1)*t.^4+xishu(2)*t.^3+xishu(3)*t.^2+xishu(4)*t.^1+xishu(5)*t.^0)
title('经验的概率密度函数图象')
figure(2)
x=-6:0.001:6
plot(x,(1/(sqrt(2*pi*dertapingfang))*exp(-((x).^2)/(2*dertapingfang))))
title('理论的概率密度函数图象')

%第四问
z=mean(m5_3)
dertapingfang=var(m5_3)
x=log(z/3)