I am using the forecast package in R to implement ARIMA Models. I am using one variable, the data is from 2016 to 2019 and it is monthly. When I look at the residual check, the 2016 residuals do not look correct. There is a flat like for 2016 and this is having an impact on tuning the model. I am looking for advice on how to fix this issue.
fit.arima <- auto.arima(RevenueDataTSTest) checkresiduals(fit.arima) ```