พี่ๆช่วยดูทีครับ (Mathlab)

% Illustration of Jacobi iteration
% (Also known as Method of Simultaneous Displacement)
%
% The goal is to determine a set of values of x1...x4 that
% satisfy the following equations...
% f1(x1,x2,x3,x4) = -2*x1 + x2 + 1.5 = 0
% f2(x1,x2,x3,x4) = x1 - 2*x2 + x3 - 0.5 = 0
% f3(x1,x2,x3,x4) = x2 - 2*x3 + x4 - 0.5 = 0
% f4(x1,x2,x3,x4) = x3 - 2*x4 + 0.5 = 0
%
% We will take an x1 out of f1 and an x2 out of f2 and so on.
% x1 = lin_g1(x1,x2,x3,x4) = (x2 + 1.5) / 2
% x2 = lin_g2(x1,x2,x3,x4) = (x1 + x3 - 0.5) / 2
% x3 = lin_g3(x1,x2,x3,x4) = (x2 + x4 - 0.5) / 2
% x4 = lin_g4(x1,x2,x3,x4) = (x3 + 0.5) / 2
%
% These are defined in files 'lin_g1.m' through 'lin_g4.m'

fprintf('\nSolution of System of Equations using Jacobi iteration\n');

x1 = input('Enter x1 estimate : ');
x2 = input('Enter x2 extimate : ');
x3 = input('Enter x3 estimate : ');
x4 = input('Enter x4 extimate : ');
maxerror = input('Enter max approx error : ');
maxit = input('Enter max # of iterations: ');

count = 0;
error = 100;
fprintf('\niteration x1 x2 x3 x4\n');

while (error > maxerror) & (count < maxit)
count = count + 1;

x1new = lin_g1(x1,x2,x3,x4);
x2new = lin_g2(x1,x2,x3,x4);
x3new = lin_g3(x1,x2,x3,x4);
x4new = lin_g4(x1,x2,x3,x4);

error1 = abs(x1new - x1);
error2 = abs(x2new - x2);
error3 = abs(x3new - x3);
error4 = abs(x4new - x4);
error = max([error1,error2,error3,error4]);

fprintf('%6i %10.6f %10.6f %10.6f %10.6f\n',...
count,x1new,x2new,x3new,x4new);

x1 = x1new; % assign new values
x2 = x2new;
x3 = x3new;
x4 = x4new;
end

รันแล้ว
input x1,x2,x3,x4,maxerror,maxit ได้ แต่มันคำนวนหาผลลัพธ์ออกมาไม่ได้ครับ ช่วยแนะนำทีครับ ช่วยดูทีครับ