error on the function of ss[Creation of State-Space Models]

when enter >> A = [0 1;-5 -2]; B = [0;3]; C = [0 1]; D = 0; sys = ss(A,B,C,D,0.25);

has below error(it is in Chinese) 'double' 类型输入参数的函数 'ss' 没有定义。

it means the double type input function 'ss' no defined. my version is 2012b

Answer 1

[Jason Zhu]

yes, you are correct. thank you anyway.

Answer 2

[Suneesh]

You might not have the Control System Toolbox installed. Check that by executing:

ver