There are 50 shops and each shop have 30000 items. Goal is to forecast the sale of item based on shop.
item_cnt_day, for this i dont see this as multi variate time series. Only shop and item ID is needed to forecast the next month data.
The question is do we need to take this as Multi time series problem and build 30000 ARMA, ARIMA, SARIMA etc models for each of the shop and items. So for 50 shops and 30000 items, there will be 50*30000 models.
What do you guys suggest to handle this problem as time series problem