knnsearch or rangesearch with annulus

For those of you familiar with Matlab's knnsearch routine (via creating a KDTree from the KDTreeSearcher routine (accessible from the Statistics and Machine Learning Toolbox)), is there a way to use to use the rangesearch and/or knnsearch comands to find the nearest neighbors of a given focal point, , say, that belong to an annulus around that focal point?

More specifically, I am trying to implement a nearest neighbor search about , and I would like to avoid being returned in the subsequent list of neighbors. After I create the KDTree (via the KDTreeSearcher command), I then use the same tree in a for-loop for many focal points. Thus, I would like to avoid creating a new KDTree for each focal point. Here are two ways to find nearest neighbors:

% construct a KDTree from some N-dimensional data
xData = randn(100,5);
xKDTree = KDTreeSearcher(xData);

% focal point
x0 = xData(1,:);

% returns the 5 nearest neighbors in the previously-constructed KDTree of the focal point x0
[IDX, D] = knnsearch(xKDTree, x0, 'K', 5);
% (note: IDX(1) = 1 and D(1) = 0)

% returns the neighbors that are located a maximum distance of 1.5 units away from the focal point x0
[IDX, D] = rangesearch(xKDTree, x0, 1.5);
% (note: IDX{1}(1) = 1 and D{1}(1) = 0)

By default, rangesearch returns the nearest neighbors that are located within some r-ball or disk of . That is, x is a nearest neighbor of if . Naturally, the focal point is a member of this set. Visually,

Yes, I am aware that I could run rangesearch (or knnsearch) once to return -many neighbors and then remove the focal point from this list. However, rangesearch and knnsearch accommodate so many search and distance/metric options that I'm curious if there is an option to use an annulus rather than an r-ball. That is, after creating xKDTree, is there a way to execute knnsearch either to find K-many nearest neighbors located a positive distance from a focal point (rather than simply a non-negative distance), or to find neighbors located in an annulus about the given focal point, ? (I am using the Euclidean norm).

Thank you for your time.

[Image Analyst]

Posting a diagram would help.

[Matthew]

(basic diagrams posted)

[Matthew]

Any ideas?