control system in matlab

you must forget to convert it into zero poles and gain model!

try this command:

c=tf([1 2],[2 4 1]);

zpk(c);

zpkdata(c)

or simple try.

[z,p,k]=zpkdata(c)

I just wanted to add that if you do a 'v' option so the call looks like this:

[Z,P,K] = zpkdata(c,'v')

the P is returned as a vector instead of a cell array. The other is perfect too.