Combined metrics with PCP_DERIVED_CONFIG

[Martin Spier <mspier@xxxxxxxxxxx>]

I know it's possible to do arithmetic operations on top of metrics to create derived metrics, like:

kernel.all.cpu.sum = kernel.all.cpu.sys + kernel.all.cpu.user

Is it possible to combine metrics into a single metric with multiple series? Like a derived metric with two or more series:

kernel.all.cpu.combined = [kernel.all.cpu.sys, kernel.all.cpu.user]

Thanks,
Martin