Hi I’m SlowlyLearningMath_houGuy, (bear with me, I am slow, but I am moving)

How to find the radius of a sphere that x amount of points fit in at a certain point distance?

(Kindof the inverse of the pointsfromvolume sop, knowing only point distance and the number of points (in VEX))

Thanks in advance.

There's many ways of doing that. Perhaps you could provide a hip file with a working example that supports your end goal.
Thereby you will get a suggested solution that fits well with your approach/context.

Check out the POP section. Made some notes for it. :-)

I would need to know the radius of a sphere to which a pointsfromvolume would produce x amount of points at with a certain point distance (0.2 in my case, because of the POP Interact values).

Hope that makes sense.

Hi,
not sure if I understood you correctly, but if you are searching for radius, where a specific ratio of fits in.
For example if you have 100 points and the ratio is 0.25 you are searching a radius, where 25 points are in the sphere with this radius.
You can try bisection method for this. Here is an example, for a 2D scatter plot (it just better for visualization it also works for 3d). Also there is usually not only one radius, but a range with minimum and maximum radius, where this condition holds.