UX Graphs: "Actions per visit" and others should be plotted on a new Y axis

[mattab]

This ticket concerns an improvement in the JS Graphs in Piwik, when plotting at least 2 metrics and comparing to each other.

For example when comparing Actions per visit and Visits, the 2 data set use the same Y axis causing one dataset to appear flat next to zero all along.

Instead for "Per visit" averaged metric, they should use a different axis than the one used to plot "totals" and sums.

See attached file

[mattab]

Attachment:
Actions per visit should be on a different Y axis with lower values.PNG

refs #3110

[eramirezprotec]

Hi, Matt! Is there documentation explaining how to show a new metric (created by developer) in a second Y-Axis on evolution graph?

Thank you