# Compute probability closeness between points in a 2D surface

##### New member
Hi all,

Sorry, in my first message, I posted this question in the Basic Probability section, and so I moved it to this section.

I have a surface (for example, a blank paper).
In this surface, I have some elements of the set "A" randomly distributed.
In this surface, I also have some elements of the set "B" randomly distributed.
I would like to understand how may elements of "B" are present within a ray X from any element of "A".

I mean something like: "for each element An, there are N% (probability_result) elements of "B". "

Is it possible?

#### Joppy

##### Well-known member
MHB Math Helper
I would like to understand how may elements of "B" are present within a ray X from any element of "A".
Possibly need more information. Without more information about the ray, it seems you want to find the diameter of B and relate it to A in some way. What are you trying to do exactly?

#### Joppy

##### Well-known member
MHB Math Helper
I think by "ray" you mean "radius"? So perhaps the question is: given a sequence of points representing circle centers ($A_n$) with radii $r$ and a collection of points $B_m$, what proportion of points $B_n$ are contained within each circle centered at $A_n$?