Pole placement design using place()

hi,

i have this m.file :

ew_place=[-8, -3, -3, -5, -6+5i, -6-5i];
K=place(A,B,ew_place);

How kann I replace ''ew_place'' with a area of Eigenvalue in the complex area? that means the Eigenvalue do not be fixed but they can be free to be located on a prescribed area in the complex area ?

[Azzi Abdelmalek]

What do you mean by The eigenvalue can be free . If they are free, with what are you going to do your pole placement?