Draw circle and ellipse in matrix

Question

Anh Mai 2021-8-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/896102-draw-circle-and-ellipse-in-matrix

评论： Anh Mai 2021-8-11

Hi all, I am using the following code to draw a circle in a given matrix. However, it only works for a squared matrix, if I change the size of the matrix to something else (for example 90 by 100), it won't work. Please help me out. I am new to MATLAB. Thank you.

nx=100;
ny=100;
domain=ones(nx,ny);
[cols rows]=meshgrid(1:nx,1:ny); 
 centerX = 40;
 centerY = 40
 radius = 15
 circle = (rows - centerY).^2 + (cols - centerX).^2 <= radius.^2
domain(circle)=2;
imagesc(squeeze(domain(:,:)));

Thanks a lot,

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Answer 1

Simon Chan 2021-8-11

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https://ww2.mathworks.cn/matlabcentral/answers/896102-draw-circle-and-ellipse-in-matrix#answer_764602

在 MATLAB Online 中打开

Modify the third line:

nx=100;
ny=90;
domain=ones(ny,nx);
[cols rows]=meshgrid(1:nx,1:ny); 
 centerX = 40;
 centerY = 40
 radius = 15
 circle = (rows - centerY).^2 + (cols - centerX).^2 <= radius.^2
domain(circle)=2;
imagesc(domain);                                    % Or keep your original code

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Anh Mai 2021-8-11

That's great, Simon. Is there any alternatives for the third line so that we can simply change the size of the domain without changing the code?. Thank you

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Answer 2

Wan Ji 2021-8-11

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/896102-draw-circle-and-ellipse-in-matrix#answer_764607

在 MATLAB Online 中打开

in line 3, do not use

domain=ones(nx,ny);

but use

domain=ones(ny,nx);

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Anh Mai 2021-8-11

Thanks Wan Ji, I am looking for an alternative that can replace the third line, so that we can only need to change the size (input of nx and ny) without changing the code.

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