If you do not include a constant (intercept) term in your model, it will force an intercept at (0,0). So if it is a straight line, to fit (x,y) data, this works:
x = randi(10, 10, 1); % Create Data
y = randi(50, 10, 1); % Create DAta
B = x(:)\y(:); % Regression Of Line Through Origin
yfit = x(:)*B; % Calculate Fitted Line
figure(1)
plot(x, y, 'bp') % Plot Data
hold on
plot(x, yfit, '-r') % Plot Fitted Regression Line
hold off
grid
axis([0 max(x) 0 max(y)])
