Controlling bubble size in bubble plots
This question has two parts:
A) relating to scale/range
relating to function/linearity
A) is not a big problem:
A workaround for controlling bubble size scale/range is to insert a dummy maximum size bubble and dummy minimum size bubble into the data, and also to clip the real data between these two levels. This forces the plotter to look at a pre-determined range, and allows for some some consistency between different charts in a series of bubble plots. It works well enough for me, but...
is a bigger problem:
Neither the diameter nor the area of the bubbles seems to be proportional (or even affine) to the data values. What is the relationship? If I remember correctly from some experiments a while back, the diameter seemed to be a slightly concave function.
Even if there is no direct method of controlling bubble size (am I just missing something?) it would be a tremendous help to just know the policy, as that would allow the user to control bubble size by carrying out the appropriate preprocessing of the data (e.g. linearlization, offset-from-dummy etc.)...