# Real, scaled sizes of bubbles in bubblechart [closed]

I'm trying to create a BubbleChart3D with sets of 4 numbers, to see which spheres overlap.

sp1= {18.7, 16.1, 10, 7};
sp2= {18.6, 14.6, 11.4, 8.5};
BubbleChart3D[{{sp1}, {sp2}}, BubbleSizes -> {7,8.5},
PlotRange -> All, ChartStyle -> Directive[ Opacity[.4]]]


However, I found this little detail in the BubbleSizes manual page:

"The sizes smin and smax specify the fraction of the diagonal of the overall chart bounding box that should be occupied by the diagonals of the bounding boxes of bubbles."

This means, in my interpretation, that I'd need to know the chart bounding box each time I make a new plot and scale appropriately. I'd imagine there's a hack-around involving a "ghost" bubble at pre-defined locations which give a constant-sized chart bounding box, after which I could scale bubbles myself. This seems like a huge hassle, and I can't imagine why Mathematica doesn't allow for hard-coding of the bubble sizes.

Does anyone have an idea of how to make bubble charts with well defined sizes (and maybe highlight overlapping areas of the spheres?)

• Welcome to Mathematica.SE! I suggest the following: 1) As you receive help, try to give it too, by answering questions in your area of expertise. 2) Take the tour! 3) When you see good questions and answers, vote them up by clicking the gray triangles, because the credibility of the system is based on the reputation gained by users sharing their knowledge. Also, please remember to accept the answer, if any, that solves your problem, by clicking the checkmark sign! Commented Jun 13, 2016 at 21:29
• BubbleChart is really only concerned with relative bubble sizes, to convey ideas about your data and facilitate its comprehension. If you need absolute bubble sizes, you will have much finer control if you generate them yourself using appropriately styled Ball primitives in a Graphics3D expression. Commented Jun 13, 2016 at 22:11
• – Jens
Commented Jun 14, 2016 at 0:45
• Commented Jun 14, 2016 at 7:14