mathanalysis202.m

数值分析的实验程序

function [x]=mathanology202(A,b)
format long
A=[1e-8 2 3
    -1 3.712 4.623
    -2 1.072 5.643];
b=[1 2 3]';
%A=[1 -1 1
%   -3 1 -2
%   3 1 -1];
%b=[2 6 12]';

A=[A b];
[m,n]=size(A);
x=zeros(m,1);
for i=1:m
    j=0;
    rr=[i:m]';
    while(1)
        y=abs(A(rr,:));
        j=j+1;
        r=find(abs(y(:,j))==max(abs(y(:,j))));
        [p,q]=size(r);
        rr=rr(r);
        if p==1|j==m
            break;
        end
    end
    [p,q]=size(rr);
    if p~=1
        flag=0;
        for j=1:p
            for k=j+1:p
                if A(rr(j),:)==A(rr(k),:)
                    flag=1;
                    break;
                end
            end
            if flag==1
                break;
            end
        end
        if flag==1
            printerror=['ERROR!','\n','No Solution!.'];
            disp(printerror);
            break;
        else
            rr=rr(1);
        end
    end
    if p==1|flag==0
        y=A(rr,i:n);
        A(rr,i:n)=A(i,i:n);
        A(i,i:n)=y;
        for j=i+1:m
            if A(j,i)~=0
                A(j,:)=A(j,:)/A(j,i)*A(i,i);
            end
        end
        for j=i+1:m
            if A(j,i)~=0
            A(j,:)=A(j,:)-A(i,:) ;
            end
        end
    end
end
if p==1
    b=A(1:m,n);
    A=A(1:m,1:m);
    x(m)=b(m)/A(m,m);
    for k=m-1:-1:1
        x(k)=(b(k)-A(k,:)*x)/A(k,k);
    end
printx=['The matrix of x is ',mat2str(x),'.'];
disp(printx);
end