There is this article where the author Michael Betancourt uses this image to convey the concept of the typical set in a distribution.
I would like to plot the typical set of a univariate or a bivariate Gaussian distribution. Thus, I should multiply the normal density by the $dq$.
But how do I get $dq$?. In 2D, for instance, should I use the derivative of the (circle) surface ($2 \pi q$)? But this would be $dV/dq$, and not just $dq$... right?
I get the intuition (the mass around a point is the product of the density times the volume around that point) but, as you can, see I'm a bit confused on how to compute this differential element.