Degree of freedom from extracted state space model

Hi all

I came to this problem. I have a simple joule heating model: an electrode sticking into a domain and flew through a current through the domain so that the mass was heated up by conductive heating effect. Then I successfully extracted the state space matrices from this model: Mc, MA, MB, C, D, (input: electrode tip voltage, output: the temperature of a point near the electrode). But, when I tried to verify the state space model (same method as introduced in the MATLAB livelink documentation, the heat_transient_axi example), I found that there's one problem that has never been discussed in the documentation: we do not know what degree of freedom or node number each state refers to, so I have no idea what initial condition to assign.

Thanks in advance for any help!

Qiyong Chen