The Web Reporter allows you to add multiple, distinct, sections to a single report. In the first section, configure your report for the graphical interface traffic data, then, when you're back at the report designer page, click the 'Add Section' button beneath first section. Then, add a new data source that grabs the the raw interface data you want
You can add multiple sections using this method, creating any kind of report you could be asked to generate. Also, as long as the data source you specified in the first section gives you the data you need for the raw data, consider adding the raw data into a custom table beneath the graph, in the first section, to save on a few CPU cycles by keeping the report to a single data source.