trying to identify the cells within a radius of a certain point (x,y)

Hi, I am new to matlab and am trying to identify the cells within a radius of a certain point (x,y) in matrix M. I know of the rangesearch function but don't entirely understand the outputs. Also, is there a way to visualize the "search radius" around a point? like plotting the search radius within the matrix. Thank you in advance

Answer 1

[KSSV]

clc; clear all ;
N = 100 ;
x = linspace(0,1) ;
y = linspace(0,1,N) ;
[X,Y] = meshgrid(x,y) ;
XX = X(:) ;
YY = Y(:) ;
radius = 0.1 ;
coor = [XX YY] ;
for i = 1:length(coor)
     % Get the distance bw ith point and rest all points
    data = repmat(coor(i,:),[length(coor),1])-coor ;
    dist = sqrt(data(:,1).^2+data(:,2).^2);
    % Arrange the distances in ascending order
    [val, pos] = sort(dist) ;
    % Pick the points which lie within radius
    neighbour = pos(val<=radius) ;
    plot(XX,YY,'.k')
    hold on
    plot(XX(i),YY(i),'*b')
    plot(XX(neighbour),YY(neighbour),'.r')
    hold off
    drawnow
end

The above can also be achieved with inbuilt command knnsearch. I hope you are looking for the same.

[Stephanie Diaz]

Thank you. Again I am new to matlab so I have a few questions; what is the purpose of "N=100" when I already have a matrix from which I want to place my circle according to a certain radius and center (cell within the matrix). Also, my matrix is too large to perform meshgrid

[yubo liu]

This is an example ,N = 100 is only the parameter of the demo ,you should apply the example to you own project ,that's all.hope to help you.

[KSSV]

You need not to use meshgrid. Name your (x,y) points as coor (Nx2 vector, where N is number of points). I suggest you to go through the knnsearch document. It is more powerful.