Why am i getting an error of too many output arguments

clc; 
clear all;
close all;
dt = [0.5 0.1 0.01];
for j = 1:length(dt)
    t = 0:dt(j):10;
    u = ones(1,length(t));
    y(1) = 0;
    dy(1) = 0;
    for i = 1:length(t)-1
        ddy(i) = u(i) - 3*dy(i) - 2*y(i);
        dy(i+1) = ddy(i)*dt(j) + dy(i);
        y(i+1) = dy(i)*dt(j) + y(i);
    end
    ya = 0.5*u + 0.5*exp(-2*t) - exp(-t);
    e = ya - y;
    figure(j*i)
    title('Unit Step Function')
    plot(t,y,'--+')
    hold on
    plot(t,ya,'--o')
    xlabel('Time(s)','Fontsize',14,'FontWeight','bold','Color','b')
    ylabel('Y','Fontsize',14,'FontWeight','bold','color','b')
    str = {'\delta(t) = ',num2str(dt(j))};
    text(t(fix(length(t)/2)),max(ya)/2,str);
    legend('Numerical Solution','Analytical Solution')
    box on
    grid on
    figure(j*(i+1))
    title('Unit Step Function')
    hold on
    plot(t,e,'--o')
    xlabel('Time(s)','Fontsize',14,'FontWeight','bold','Color','b')
    ylabel('error','Fontsize',14,'FontWeight','bold','color','b')
    e_max(j)= max(abs(error));
    box on
    grid on
end


% I get the error in the line e_max(j) = mac(abs(error));

Answer 1

[Walter Roberson]

    e_max(j)= max(abs(error));

You do not have any variable named error, so you are calling the function error() expecting an output but error() does not define any outputs.