Thanks for posting.
It would be great if this functionality could be provided.
I don't know how bubble size is currently determined, but I am guessing you have a maximum bubble size, say 100px, and then all bubbles are drawn relative to this max bubble pixel size based on on the each bubble's size as compared to the largest bubble size. Seems like you could provide an option for maximumRadius when building the chart, and then scale all bubbles relative to this "base size":
Specify maximumRadius: 10
Largest bubble size in jqchart = 100px (for example), so any bubble with a radius of 10 would be drawn at 100px
Date1
Radii:
1, 3, 5, 7
Size:
(1/10)*100 = 10px, (3/10)*100 = 30px, (5/10)*100 = 50px, (7/10)*100 =70px
Date2:
Radii:
2, 3, 6, 10
Size:
(2/10)*100 = 20px, (3/10)*100 = 30px, (6/10)*100 = 60px, (10/10)*100 = 100px
If that made any sense at all.
That way, when you toggle from Date1 to Date2, the bubbles change size relative to a base size rather than change size relative to the largest and smallest bubble on the chart (if that is your current logic).