function f = resonant_jump(A,kolor)

%amplitude of the step function A > 0
T = 20;
dt = 0.05;
t = 0:dt:T;
x0 = [0; 0];

OPT = odeset('RelTol',1e-6,'AbsTol',[1e-6]);

[t,x] = ode45(@nonlin_oscillator,t,x0,OPT,A);

uh = plot([-0.1 t(1) t(end)], [0 A A],'--','Color',num2str(kolor),'LineWidth',2);
hold on
yh = plot(t,x(:,1),'Color',num2str(kolor),'LineWidth',2);

legend([uh, yh],'Input','Output','Location','best')
set(gca,'FontSize',16,'FontWeight','b','FontAngle','i', ...
    'Xlim',[t(1) t(end)])
xlabel('Time');

f = x(:,1);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function [dx] = nonlin_oscillator(t,x,u)

dx = zeros(2,1);

dx(1) = x(2);
dx(2) = -x(1) - 2*(1-u)*x(2) + u;