Matlab Forum

I got a program which incorporates 5 responses of a control systems I'm done with the 4 responses i only need the parabola response which i cannot get
 
I need help with the program in showing the parabola response of a transfer function given that the numerator and the denominator of the system is the input and then shows the parabola response.
 
This is a part of the program
 
 num=get(handles.edit1,'string');
den=get(handles.edit2,'string');
num=str2num(num);
den=str2num(den);
[numCL,denCL]=cloop(num,den);
t=0:0.1:10;
axes(handles.axes1)
sys=tf(numCL,denCL);
? <<<<< for parabola equations
Plot(What?)for parabola plot

I need a parabola response please help me
and thank for the time