However, if you add a series of data points to a spreadsheet, Excel doesn't know to include these on an existing chart. To include this data, you must manually add the series to the chart.

You don't need Microsoft Excel to chart data in an existing Excel file; you can simply import that data and chart it entirely in Microsoft Word. Follow these steps: ...

How to Add Two Lines to a Powerpoint Chart. "Presenters are usually guilty of including too much data in their on-screen charts," says Garr Reynolds, author of Presentation Zen.