Add additional line to linechart

[jbrodmann]

Hi, I have a linechart with two dimensions: a date for the x axis and merchants that are displayed as separate lines. The y-axis is a measure wich counts (e.g.) the offers for each merchant.

Is there any way to add a additional line to this chart wich shows the average value over all merchants?

[jerifortune]

Combo chart allows you to add a third axis. This will give you additional line if you want it not to be based on y-axis.