Hi, I could use some guidance from seasoned Gretl users. I am trying to estimate the trend component of a univariate financial time series using an unobserved components model and the Kalman Filter using the kalman command. I'm new to Gretl and it's been some time since I've even looked at state space models. Here are my equations: Let x(t) be the univariate monthly financial time series data I have. x(t) = w(t) + y(t) where w(t) is the trend and y(t) is the cycle w(t) = x(t-1) + e(t) y(t) = rho*y(t-1) + u(t) e(t) and u(t) not correlated In the notation of the Gretl users guide, I believe I have the following matrices for the kalman command: H = { 1 ; 1} F = {1, 0; 0, rho} Q = {var(e), 0; 0, var(u)} I'm not sure what to do with the observation matrix -- this is where I'm stuck. Also,should I specify statevar and obsvar as scalars instead? I have a univariate time series, x(t). Once I have the system set up I could proceed to estimate rho, var(e) and var(u), then calculate the trend forecasts. Any guidance would be greatly appreciated.