How to plot the sum and the individual components in Graphite?

Question

We collect CPU-time statistics for each host here:

• stats.hostname.cpu.system
• stats.hostname.cpu.user
• stats.hostname.cpu.waiting

How can I plot their sum with individual components shown in different colors? Something like this:

Answer 1

Ok, adding areaMode=stacked to the URL seems to do the trick...

Still would like a Graphite-expert to comment -- a surprising shortage of them here.