I looked at the RadDiagram options, but it doesn't have anything that compares to a circular relationship chart.  Here's an example:

https://www.codeproject.com/KB/silverlight/342715/screenshot2.png

Part of this article:

https://www.codeproject.com/Articles/342715/Plotting-Circular-Relationship-Graphs-with-Silverl

I gave some thought at trying to rewrite the code into WPF, but I've got too many other irons in the fire.  Figured I'd ask as this sort of visualization control doesn't appear in your current collection.  I have a project that could benefit from displaying weighted relationships in such a manner, but my choices are either do something sub-par with the RadDiagram option, write one myself, find another controls collection and port everything, or leave the feature out for now.  I'm going for the leave it out option for the moment, and see if your UI wizards can come up with something...

Just as a use case, one of the reasons for wanting this is to diagram conversations between individuals in email messages.  Being able to show who's talking to whom and how frequently using one of these charts for visualization allows you to quickly find patterns...