满意答案

a9hfg6i6

2013.06.04

采纳率：54%    等级：12

已帮助：9403人

我曾经写过的一个程序，

包含了画点，拟合，误差评估等

你相应的删减一些，

就能得到你需要的东西了。

希望能看的懂：

关键就一个函数：

a=polyfit(x,y,n);

请去matlab:

help polyfit

保证10分钟弄回自己的程序。

求人不如求己

% to find the least_squares fit for an input data set.

% to make a straigh line,and print it out.

% to deteming the constant m,b of y=mx+b.

%

%

clc; %clear the command window

clear;%clear all the variable has been defined

disp('----this program find the least_sqares fit of an input data set');

disp('---- as the form of y=a1*xn+a2*x(n-1)+....a(n)*x1+a(n+1)');

disp('------------starting!----------------');

%input data num

%input times of poly

x=input('enter the array of x like [1,2,3,4,....]:');

y=input('enter the array of y like [1,2,3,4,....]:');

n=input('enter times of polynomial like 2 :')

a=zeros(n+1);

%to count how many data in x

row_cloum=size(x);

m=row_cloum(2);

for i=1:1:m

plot(x(i),y(i),'bo');

hold on;

end

%calculate a

a=polyfit(x,y,n);

y_best=0;

%least squraus of ybest

%%plot the data input data as blue circles

% plot the line in red '-'

%create the fitted line of figture

xmin=min(x);

xmax=max(x);

t=xmin:0.01:xmax;

for i=1:(n+1)

y_a=(a(i)*(t.^((n+1)-i))); %element of y_poly_array

y_best=y_best+y_a; %sum them

end

% r the error array

for k=1:m

r_sum=0;

y_kbest=0;

for i=1:(n+1)

y_k(i)=(a(i)*(x(k).^((n+1)-i))); %element of y_k= ploy(xi)

y_kbest=y_kbest+y_k(i); %sum them ploy(xi)

end

r_sum=(y(k)-y_kbest)^2+r_sum;

end

%the poly is:

disp('the poly is y=a1*xn+a2*x(n-1)+....a(n)*x1+a(n+1):')

disp('and the array A is A=:');

disp(a);

disp('the (y_best-y)^2 is R= :')

disp(r_sum);

%figture

ymin=min(y_best);

ymax=max(y_best);

axis=([xmin,xmax,ymin,ymax]);

%set plot settings

%add a title and legend

plot(t,y_best,'r-','LineWidth',2);

%hold off;

title('\bf least-squares fit y=a1*xn+a2*x(n-1)+....a(n)*x1+a(n+1)');

xlabel('\bf\itx');

ylabel('\bf\ity');

legend('input data','fitted line',4);

grid on;

print -dtiff lsq_fit.tif;

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