Making circular agglomerates using equation of circle

Question

Chris Dan 2022-3-30

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https://ww2.mathworks.cn/matlabcentral/answers/1684154-making-circular-agglomerates-using-equation-of-circle

编辑： Chris Dan 2022-3-31

采纳的回答： Chris Dan

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Hello,

I am trying to make circular agglomerates using this code, but it is plotting rectangles instead.

close all; clear all;

%% Data for Agglomerates

N = 5; % number of circles

a = 50; % lowest diameter of circles

b = 60 ; % highest diameter of cicles

Diam = a + (b-a).*rand(N,1);

Diam = round(Diam);

aaa= 1; % minimum x and y coordinate limit for circles

bbb= 5 ;% maximum x and y coordinat limit for circles

M=2 ;

Axes= zeros(N,M);

Axes(:,1)=aaa+(bbb-aaa)*rand(N,1);

for k=2:M

a=randperm(N);

Axes(:,k)=Axes(aaa,1);

end

Axes_Label ={'X axis','Y axis'};

Data_agglo = [Diam Axes];

Data_Label ={'Diameter','X axis','Y axis'};

%% Plotting Agglomerates in 2D

R = Diam ./2;

f = figure('visible','on');

for i =1:1:size(Data_agglo,1)

p = linspace(Data_agglo(i,2),Data_agglo(i,3),10);

[X,Y] = meshgrid(p,p); % box mesh

active = (X.^2 + Y.^2 <= R(i)^2);

plot(X(active),Y(active),'o','MarkerFaceColor','blue');

hold on

end

hold on

the problem is with the active line or with the whole algorithm.Does anyone knows?

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Answer 1

Chris Dan 2022-3-31

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close all; clear all;
%% Data for Agglomerates
N = 100; % number of spheres
a = 1; % lowest diameter of sphere
b = 100 ; % highest diameter of sphere
Diam = a + (b-a).*rand(N,1);
Diam = round(Diam);
aaa= 1;  % minimum x and y coordinate limit for spheres
bbb= sum(Diam) ;% maximum x and y coordinat limit for sphere
M=2  ;
Axes= zeros(N,M);
Axes(:,1)=aaa+(bbb-aaa)*rand(N,1);
for k=2:M
    aaa=randperm(N);
    Axes(:,k)=Axes(aaa,1);
end
Axes_Label ={'X axis','Y axis'};
Data_agglo = [Diam Axes];
Data_Label ={'Diameter','X axis','Y axis'};
R = Diam ./2;
s = sum(Axes);
%% Plotting Agglomerates in 2D
f = figure('visible','on');
for i =1:1:size(Data_agglo,1)
    
    p = linspace(-Diam(i),Diam(i),200);
    
    [X,Y] = meshgrid(p,p); % box mesh
    active = X.^2 + Y.^2  <= R(i)^2 ;
    plot(Data_agglo(i,2)+X(active),Data_agglo(i,3)+Y(active),'o');
    hold on
end

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Answer 2

Geoff Hayes 2022-3-30

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@hamzah khan - I think the problem is that diameters of your circles are too large given the limits you impose on your x and y variables. The diameter appears to be in the interval [50,60] yet your x and y limits are in the interval [1,5]. This would mean that all values in the meshgrid result would be considered to be "active" as per

active = (X.^2 + Y.^2) <= R(i)^2;

and so you would be plotting a rectangle instead of a circle. For example, the following code would create a circle given a radius of 2.5 with x and y in the interval [-10,10]

p = linspace(-10,10,1000);
[X,Y] = meshgrid(p,p); % box mesh
active = (X.^2 + Y.^2)  <= 2.5^2;
plot(X(active),Y(active),'o','MarkerFaceColor','blue');

Note also how p is an array of 1000 elements. You could use fewer and I recommend that you experiment with this number. I think that the 10 you had is too small and so you won't necessarily get the circular shape that you are hoping for.

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Geoff Hayes 2022-3-31

@hamzah khan - which part of your code determines or indicates the centre of the circle?

Chris Dan 2022-3-31

编辑：Chris Dan 2022-3-31

在 MATLAB Online 中打开

Hii

Geoff Hayes

I found the answer

close all; clear all;
%% Data for Agglomerates
N = 100; % number of spheres
a = 1; % lowest diameter of sphere
b = 200 ; % highest diameter of sphere
Diam = a + (b-a).*rand(N,1);
Diam = round(Diam);
aaa= 0;  % minimum x and y coordyinate limit for spheres
bbb= sum(Diam) ;% maximum x and y coordinat limit for sphere
M=2  ;
Axes= zeros(N,M);
Axes(:,1)=aaa+(bbb-aaa)*rand(N,1);
for k=2:M
    aaa=randperm(N);
    Axes(:,k)=Axes(aaa,1);
end
Axes_Label ={'X axis','Y axis'};
Data_agglo = [Diam Axes];
Data_Label ={'Diameter','X axis','Y axis'};
R = Diam ./2;
s = sum(Axes);
%% Plotting Agglomerates in 2D
f = figure('visible','on');
for i =1:1:size(Data_agglo,1)
    
    p = linspace(-Diam(i),Diam(i),200);
    
    [X,Y] = meshgrid(p,p); % box mesh
    active = X.^2 + Y.^2  <= R(i)^2 ;
    plot(Data_agglo(i,2)+X(active),Data_agglo(i,3)+Y(active),'o');
    hold on
end