# 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?)

## closed as off-topic by MarcoB, user9660, Öskå, m_goldberg, Mr.Wizard♦Jun 16 '16 at 12:53

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "This question arises due to a simple mistake such as a trivial syntax error, incorrect capitalization, spelling mistake, or other typographical error and is unlikely to help any future visitors, or else it is easily found in the documentation." – MarcoB, Community, Öskå, m_goldberg, Mr.Wizard
If this question can be reworded to fit the rules in the help center, please edit the question.

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• 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. – MarcoB Jun 13 '16 at 22:11
• – Jens Jun 14 '16 at 0:45
• – Ymareth Jun 14 '16 at 7:14