beta(zeta) := sqrt(1-zeta^2);
theta(zeta) := atan(beta(zeta)/zeta);
h_under(wt) := 1 - beta(0.5)^-1*exp(-0.5*wt)*sin(wt*beta(.5)+theta(0.5));
load(draw);
draw2d(dimensions=[800,300],terminal=svg,
	 user_preamble="set mxtics; set mytics;",
	 grid=true, yrange=[0,1.5], xlabel="omega t",xtics=1,
	 key="",points_joined=true,
	 head_both=true,head_length=0.1,line_width=0.5,
	 line_type=dots,nticks=10,color=black,points([ [3.6,1],[3.6,1.16] ]),
	 vector([0,1.2],[3.6,0]),label(["t_p",2.0,1.25]),
	 label(["M_p",3.8,1.05]),
	 vector([2.42,1],[-2.42,0]),label(["t_r",1.21,1]),
	 vector([1.29,0.5],[-1.29,0]),label(["t_d",0.64,0.5]),
         line_width=1.5,line_type=solid,ylabel="Step response",nticks=100,
         color=blue,explicit(h_under(wt),wt,0,10)
	);