Making a Legend/Key in GraphViz

Question

Hi,

I’d like to include a legend or key in my GraphViz diagram, something like the mock-up below. I’m having trouble figuring out what code to use though; the best I can get are the attempts in the second graphic. I also want to put it in a corner, but the only coord I know for sure is the bottem-left: pos="10,10!".

Does anyone know how I can get this to work?

Thanks a lot.

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Wanted:

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Attempted:

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