this is my first ever question on a website i use frequently!
This time series has given me much trouble over the last couple of days even after extensive googling, I suppose with TS theres no two series that look the same, hence my confusion!
I have the following ACF and PACF plots for my data:
After modelling NUMEROUS models in R (ARMA(p,q), with all combinations of p=0,1,2,3,4 and q=0,1,2,3,4) and looking at their theoretical acf plots, it seems R's auto.arima gave the best model with p=q=2.
But in my work, i don't want to just say i used R and inferred nothing from the ACF plots haha!
I understand that the slightly significant PACF at lag 1 indicates an AR component(?) and that as both plots 'slope off' it suggests a ARMA(p,q) model, but is there anything else im missing????
Also; the ts (in my eyes) seems seasonal, however ironically, no amount of differencing makes a difference, the plot still looks the same no matter what d equals. (R also tells me its not seasonal)
- What does the ACF plots tell me (main)
- Am i right in not differencing the data
Thanks a bunch!!