求高手帮忙看看下面的程序怎么改  牛顿迭代法  求解后现实矩阵奇异，跪求高手

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%首先建立函数fun

%储存方程组编程如下将fun.m 保存到工作路径中:

function f=fun(x);

%定义非线性方程组如下

%变量x1 x2 x3

%函数f1 f2 f3

syms x1 x2 x3 x4 x5 x6 x7

f1=10*(348.51-269.62)-x1*(275.74-x2);

f2=10*(669.98-348.51)-x1*(x3-275.74);

f3=10*(682.43-669.98)-x1*(418.53-x3);

f4=10*(x4-627.85)-x5*(x6-100.11);

f5=10*(627.85-271.39)-x5*(100.11-x7);

f6=10*(271.39-268.93)-x5*(x7-104.29);

f7=x4-682.43-0.8*(682.43-648.38);

f=[f1 f2 f3 f4 f5 f6 f7];

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%建立函数dfun

%用来求方程组的雅克比矩阵将dfun.m保存到工作路径中:

function df=dfun(x);

%用来求解方程组的雅克比矩阵储存在dfun 中

f=fun(x);

df=[diff(f,'x1');diff(f,'x2');diff(f,'x3');diff(f,'x4');diff(f,'x5');diff(f,'x6');diff(f,'x7')];

df=conj(df');

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%编程牛顿法求解非线性方程组将newton.m 保存到工作路径中:

function x=newton(x0,eps,N);

con=0;

%其中x0为迭代初值eps 为精度要求N 为最大迭代步数con 用来记录结果是否收敛

for i=1:N;

f=subs(fun(x0),{'x1' 'x2' 'x3' 'x4' 'x5' 'x6' 'x7'},{x0(1) x0(2) x0(3) x0(4) x0(5) x0(6) x0(7)});

df=subs(dfun(x0),{'x1' 'x2' 'x3' 'x4' 'x5' 'x6' 'x7'},{x0(1) x0(2) x0(3) x0(4) x0(5) x0(6) x0(7)});

x=x0-f/df;

for j=1:length(x0);

il(i,j)=x(j);

end

if norm(x-x0)

con=1;

break;

end

x0=x;

end

%以下是将迭代过程写入txt 文档文件名为iteration.txt

fid=fopen('iteration.txt','w');

fprintf(fid,'iteration');

for j=1:length(x0)

fprintf(fid,' x%d',j);

end

for j=1:i

fprintf(fid,'\n%6d ',j);

for k=1:length(x0)

fprintf(fid,' %10.6f',il(j,k));

end

end

if con==1

fprintf(fid,'\n 计算结果收敛！');

end

if con==0

fprintf(fid,'\n 迭代步数过多可能不收敛！');

end

fclose(fid);

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%运行程序

%在matlab中输入以下内容

newton([0.1 0.1 0.1 0.1 0.1 0.1 0.1],0.000001,20)

[img]file:///C:/Users/Administrator.PPTV3-20120830L/AppData/Roaming/Tencent/Users/310498102/QQ/WinTemp/RichOle/A3[(5U3BU%605%60[35%60%7DK4DQKX.jpg[/img]

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