Intro
An Overlay Bar chart is similar to a standard Stacked Bar chart except that instead of being stacked, all series items begin from the baseline, so overlapping of series items occurs in a category when multiple series are present. In its initial non-rollover state, an Overlay chart is rather meaningless, as shown in the following example:

Powering Overlay Bar charts
An Overlay Bar chart requires three data columns or rows from your DataSet—one for categories, one for the series in each category, and one for values. For information about value, category, and series data, see Understanding Chart Data. In the Analyzer, you choose the columns containing the data for your Overlay Bar chart. For more information about choosing data columns, see Applying DataSet Columns to Your Chart. For more information about formatting charts in the Analyzer, see KPI Card Building Part 2: The Analyzer. The following graphic shows you how the data from a typical column-based spreadsheet is converted into a vertical Overlay Bar chart:
