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

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NA 2021 年 11 月 30 日
コメント済み: NA 2021 年 12 月 1 日
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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### 採用された回答

Matt J 2021 年 11 月 30 日
At the very end of the the Examples tab of
you will find examples for how to plot circles and rotated ellipses.
##### 1 件のコメント表示非表示 なし
NA 2021 年 12 月 1 日
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

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