I am running a TS model & below are my ACF & PACF plots... In theory if the ACF plot is significant after Pth lag & PACF shows some geometric decay we can infer it is a MA series but my output is a little confusing where it doesnt follow any geometric decay for the PACF plot & also ACF is significant after 0th lag..How can I infer the model parameters/orders from this plot. Please advise.ACF Plot
Your acf and pacf plot is ambiguous. The paradigm you are trying to follow to identify the SARIMA model sometimes works when 1) there are no one-time pulses in the data 2) there are no seasonal pulses in the data 3) there are no level/step shifts in the data 4) there are no local trends in the data 5) the underlying (waiting to be discovered ) model generates errors that has constant variance 6) the underlying model has constant parameters over time.
A more robust paradigm/procedure to follow is suggested here
If you post your data , I will try and help further.