I am building a forecasting model sing R utilizing stl() function. I have monthly data for 2 years, that's 24 observations, 2 period.
Now stl() won't allow me to decompose my data saying that I have less than the required minimum observation. I check the code and yes, it needs to be 24 + 1 or 2 period + 1.
My question is why it needs extra observation? decompose() function needs only at least 2 period.