MATLAB: How to fix this error

Control System Toolboxstep poles zeros model

Hi all!
How can I fix this error?
sys=tf([1 1 1 1],[1 1]);
t=0:0.1:10;
step(sys,t)
??? Error using ==> DynamicSystem.step at 84 Cannot simulate the time response of models with more zeros than poles.
I know that my system is unstable but how can I receive an "unstable" graph for this system on my axes?

Best Answer

Just FYI the following code won't provide the same graph has the step function, it just plots the function having s as the variable, the step fuction just works for proper systems (n poles >= n zeros).
"Impulse response":
syms s
TFC=evalc('tf([1 1 1 1],[1 1])');
[a b] = strread(TFC, '%s %s', 'delimiter',char(10));
num=sym(char(a(2)));
den=sym(char(a(3)));
ezplot(num/den,[0 100])
"Step response":
syms s 
TFC=evalc('tf([1 1 1 1],[1 1 0])');
[a b] = strread(TFC, '%s %s', 'delimiter',char(10)); 
num=sym(char(a(2))); 
den=sym(char(a(3))); 
ezplot(num/den,[0 100])
The scales aren't the same like you get with the step function.
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