Plotting ellipses around the data points and circle around the cluster points

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NA 2021-11-30

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1599644-plotting-ellipses-around-the-data-points-and-circle-around-the-cluster-points

评论： NA 2021-12-1

I have these points xy

xy = [10 -10; 1 0; -1 0; 0 -1; 0 1 ;11 -10; -1 -1];
scatter(xy(:,1),xy(:,2))
grid on
xlim([-20 20])
ylim([-15 15])

I want to mark a clusters of the data by circle. This is the function that I used incircle()

[C,R] = incircle(A(:,1),A(:,2));
viscircles(C,R,'color','b')

It does not plot proper circle around the data.

After this want to draw ellipse around all data plotEllipses

plotEllipses([0, 0], [10, 0.5])

But I dont know how to rotate ellipse

The result should be:

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Answer 1

Matt J 2021-11-30

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1599644-plotting-ellipses-around-the-data-points-and-circle-around-the-cluster-points#answer_844089

At the very end of the the Examples tab of

https://www.mathworks.com/matlabcentral/fileexchange/87584-object-oriented-tools-for-fitting-conics-and-quadrics

you will find examples for how to plot circles and rotated ellipses.

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NA 2021-12-1

在 MATLAB Online 中打开

Thank you. I'd like to make sure that I need to use incircle() function, for finding the center.

Also, I should run ellipticalFit.groundtruth two times to draw circle and ellipse.

This is the code I used

A = [10 -10; 1 0; -1 0; 0 -1; 0 1 ;11 -10; -1 -1];
[C,R] = incircle(A(:,1),A(:,2));
Cx = C(1);
Cy = C(2);
angle = -41;       %Rotation angle in degrees
[a,b] = deal(18,2);  %Major and minor axis radii
gtobj=ellipticalFit.groundtruth(A', [Cx,Cy],[a,b],angle); %Ground truth object
[hTruth,hData]=plot(gtobj,{'Color','m','LineWidth',2},...
                          {'MarkerFaceColor','c','MarkerEdgeColor','k'}); %Visualize ground truth
                      
hold on
gtobj=ellipticalFit.groundtruth(A', [Cx,Cy],[2,2],angle); %Ground truth object 
[hTruth,hData]=plot(gtobj,{'Color','k','LineWidth',1},...
                          {'MarkerFaceColor','c','MarkerEdgeColor','k'}); %Visualize ground truth
                      
xlim([-20 20])
ylim([-15 15])
grid on