MATLAB: Stepinfo

Control System ToolboxfunctionsMATLAB

why stepinfo function don't give me any numerical results for
>> q=tf([1 2 ],[ 1 2 3 4 5 7]); >> stepinfo(q)
ans =
        RiseTime: NaN
    SettlingTime: NaN
     SettlingMin: NaN
     SettlingMax: NaN
       Overshoot: NaN
      Undershoot: NaN
            Peak: Inf
        PeakTime: Inf

Best Answer

1 and 2 are roots of the numerator and are also roots of the denominator. Therefore at 1 and 2, the value of the function is not simply one of the infinities but is instead 0/0 = NaN . Transfer functions that have point singularities like this do not have defined values for the parameters you are looking for.
Related Question