Hi
1) In the present Matlab kalman_filter.m suite, the steady state conversion is checked as notsteady = max(max(abs(K-oldK))) > riccati_tol; where K = P(:,mf)*inv(F); is the gain matrix and the first Kold=0;
One problem with that is that, however unlikely, the first K may be sufficiently small, close to 0, leading to a wrong inference that the conversion to steady state occurred in the first step. To avoid that (unlikely) situation, Kold may be set to Inf or some other very large value instead or, the check should take place only if t>1, though setting the first Kold=Inf is a more straight forward change in Matlab kalman_filter.m.
2) Though Harvey (1989) and some other authors assumes convergence when the whole P matrix converges (and the whole P convergence was checked in the initial C++ Kalmn Filte implementations) I wander if we should implement the above gain matrix convergence as a sufficient criteria in the new C++ KalmnFilter instead.
If so, I can make checks work for t>0 only.