I'm trying to understand what the relationship is between the size of bubbles in a bubble chart (EDIT: more precisely a grouped bubble chart) and the underlying values. I would expect the area of the bubbles to be in a linear relationship with the values they represent, but I have a chart in which this is clearly not the case.
Below is a bubble chart on a small data set of movie ratings. The value for the second bubble (1940-1945) is 3. The value for the second-to-last bubble is 309, i.e., 100 times more. However the bubble's area looks roughly 10x as big as the first one, clearly not 100x as big.
Is this the expected behavior? Is this a bug?
EDIT: I think this is a bug. I get very different results depending on the base radius I set for the bubbles. When I set a base radius of 10, I get same-sized bubbles:
Whereas when I set a very small OR very large base radius, I get more differentiated (and realistic) results. Here is for base radius = 1:
I am using Dataiku 4.1.0. The same behavior can be observed on tutorial 103's customers_orders_joined dataset for base radius = 10: