## Often want to generate random initial conditions for a simulation, e.g. initial position & velocity.

## Must take care when using transformations, since you may not get the distribution you expect.

## For example, to fill a flat disk of radius

*R*with random points is it better to:- Fill a square and reject points with
*x*2 +*y*2 >*R*2? - Choose random and
*r*then set*x*=*r*cos,*y*=*r*sin?

- Fill a square and reject points with