I'd like to add custom data to the data I plot in a QCPGraph.
I notice that QCPGraph inherits QCPGraphDataContainer = QCPDataContainer< QCPGraphData >.

How can I manage to add custom data to QCPGraphData (by subclassing for example) without making my own QCPGraph inheriting the newly class ? Because at the end the new QCPGraph class will be exactly the same as QCPGraph given that it won't use the metadata itself.

Currently what I'm doing is keeping a side map that links QCPGraph key to the metadata, but I think this wastes memory.