I am trying matlab code for uncontrollable states. I entered 6x6  A matix  and 6x1 B matrix randomly. but controllable matrix has a full rank. It should be rank deficient in order to find P column vector and and transformed A and B matrix. 

What should i change to make controllable matrix rank deficient? I did make some changes in A and B matrix but still controllable matrix is of full rank. 

Should i keep changing A and B matrix or Is there any other way