I want to (uniformly) sample two coordinates `x`

, `y`

that lie within a circle, which are inputs to a stochastic function. It’s easiest to sample the `r`

and `theta`

coordinates and transform these to the Cartesian ones, but I’d like to apply HMC to find the posteriors for `x`

and `y`

. As I understand it this means they need to appear in `pyro.sample()`

statements.

What’s the best way to go about this? Do I need to use HMC to sample `r`

, `theta`

and map these to samples from `x`

and `y`

later?