Black Label kindly shared their grouped X-axis plugin: https://github.com/blacklabel/grouped_categoriesLjubisa Nikolic commented
ok, I will do thatLjubisa Nikolic commented
Actually the export function doesn't work with this plugin. The data witch is in the lower row of the X-axis doesn't appear in the exported image.
Furthermore - after the export, the chart changes so that the second row is compressed, like this: http://imgur.com/1itWdxw
I can supply the code on jsfiddle - if needed!