Plotting 2D arrays of concentric circles in a meshgrid.

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Viron Gil Estrada 2018-3-15

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/388415-plotting-2d-arrays-of-concentric-circles-in-a-meshgrid

编辑： Viron Gil Estrada 2018-3-15

I now have two separate codes for plotting N by N arrays of solid circles and for plotting concentric circles.

 %Plotting  an N by N arrays of circles
 clc; clear;
 n_circles = 4;                    % Define the number of circles to be plotted
 R = 63;                      % Define the radius of the basic circle
 Len=1024;
 M=zeros(Len);               % Create the hole mask
 % Get the indices of the points inside the basic circle
 M0 = zeros(2*R+1);             % Initialize the basic mask
 I = 1:(2*R+1);             % Define the x and y coordinates of the basic mask
 x = (I - R)-1;
 y = (R - I)+1;
 [X,Y] = meshgrid(x,y);      % Create the mask
 A = (X.^2 + Y.^2 <= R^2);   
 [xx,yy]=ind2sub(size(M0),find(A == true));  
 %plot
 for ii=1:n_circles
    for jj=1:n_circles
      MidX=Len/2+(ii-n_circles/2-0.5)*(2*R);
      MidY=Len/2+(jj-n_circles/2-0.5)*(2*R);
 %       [MidX MidY]
      M(sub2ind(size(M),MidX+xx-R-1,MidY+yy-R-1))=1;
    end
 end
 figure(1)
 imshow(M)

The second code below is for generating concentric circles using meshgrid.

 N=1024;  % some size of grid
 if mod(N,2) % odd vs even matrix sizes
        [x,y] = meshgrid(-(N-1)/2:(N-1)/2);
 else
        [x,y] = meshgrid(-N/2+1:N/2);
 end
 x0=0; y0=0; % assuming the circle is always at the origin, but wew can modify this if needed 
 % Rings between `r1` and `r2`
 f = @(r1,r2) (x-x0).^2+(y-y0).^2<=r2^2 & ...
             (x-x0).^2+(y-y0).^2>=r1^2;
 R = f(70,90)+f(100,120)+f(130,150)
 imagesc(R)
 axis equal