Grouping and Aggregation

Essential Chart uses Essential Grouping to manipulate data to provide certain cumulative charts from instance data. The chart below shows trading volume for issues on a given day. The data in this case is a ticker-type data set that shows a time stamp, a volume value, a symbol and a price. To get the cumulative chart from this data, Essential Chart first groups the data by symbol, and then aggregates the data to get the total volume on a symbol by symbol basis.'