Overlays place two y-axes on the same chart, one of which is placed at the left of the chart and one at the right.
Each axis can be scaled differently and your data series can be plotted against either of the axes.
To work with overlays:
Choose Overlay from the menu which appears
when you click the Chart button.
Select the option you require from the Overlay dialogue box.
Choose one of Bar-bar,
Bar-line,
Line-Line or
Scatter-Scatter.
Fireworkz automatically divides the data series into two and plots
the first half on the left axis and the second half on the right axis.
If a series appears on the wrong half of the chart, select it and change its status
in the Overlay section of the Series dialogue box.