Identifying data to be aggregated
To identify the data that you are going to aggregate in the initial dataset that you have created, it is important to understand the story that you are trying to tell about the data. Some items will need to be counted, some will need to be summarized, and some will need to be aggregated by summarizing and counting. For example, if you are interested in doing an analysis of the data showing how many times an item has been ordered, then this would be an example of when you would aggregate the data by performing counts. If you are looking at data to see how many sales have occurred or the profits that have been made, this would be an example of summarizing the data. In addition, you may be interested in the average profit for a time period or the earliest and latest that an order has been delivered.
With these aggregations in place, the size of the dataset will be reduced, and you will be able to perform several other calculations based on these aggregations...