I agree, the type of display you have chosen is most informative and any suggestion I make will just not be as good.
Here are some ideas to how you can solve the issue at hand.
1. I have not seen any of your code so I will explain a few things. We have two types of series - categorical and scatter. For instance BarSeries and PointSeries are categorical, where one of the axes is categorical. Say you want to plot fruit count - Bananas 50, Apples 20, Oranges 25. Scatter series have two numerical axes.
The categorical series have a CombineMode, where the scatter do not. In the images you attached, the Probability (horizontal values) are always integer. If this is the case, and all Probabilities are integer, you can use a categorical chart with a small work-around to ensure points do not overlap. I have demonstrated this in the project I attached. The work around is to use BarSeries (because the Cluster CombineMode is not implemented for the PointSeries) with a custom template to mimic a Point and using a dummy series to ensure that there are no missing values (such as Probability=2 in my example).
Surely, this will not work if the probabilities are not integer, but double.
2. Another option is to set a tooltip for the item's label. This way, the user can see that there are two labels and hover over one of them, to get info. (Of course, an option would be to plot all needed data in the label.) I will not go any deeper here, hoping the first suggestion is a feasible solution.
3. Another option is for you to implement your own track-ball or tooltip features and show information for all overlapping items. You can check out an example of a trackball-like annotations in our sdk samples here
Let us know how it goes.
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