用列主元法求方程组的解.m

本程序是用MATLAB编写

clc
clear
a=[0.012 0.01 0.167 0.6781;1 0.8334 5.91 12.1;3200 1200 4.2 981]
 %a=[1 1 2 4;5 6 4 8;1 5 7 2]
 %a=[2 -3 1 -3;-3 5 -7 4;1 -2 3 -4]
m=3;n=4;
   for j=1:1:m
        x=j;
        y=j;
    for z=j+1:1:m
        if abs(a(x,y))<abs(a(z,j))
            x=z;
            y=j;
        end
    end
    if x~=j|y~=j
        for z=1:1:n
            temp=a(j,z);
            a(j,z)=a(x,z);
            a(x,z)=temp;
        end
    end    
     for i=j+1:1:m
      g=-a(i,j)/a(j,j);
	  for k=j:1:n
          
	      a(i,k)=g*a(j,k)+a(i,k);
       
      end 
      
  end
     
end
disp('-------------------------------------');

disp(a);

for j=m:-1:1
    for i=j-1:-1:1
       l=-a(i,j)/a(j,j);
       for k=j:1:n
           a(i,k)=l*a(j,k)+a(i,k);
          
           
           
       end
   end
   disp(a);
   
end



for i=1:1:m
    t=a(i,i);
    for j=i:1:n
        a(i,j)=a(i,j)/t;
    end
end
disp(a);