Draw circle and ellipse in matrix

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Anh Mai
Anh Mai on 11 Aug 2021
Commented: Anh Mai on 11 Aug 2021
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,

Answers (2)

Simon Chan
Simon Chan on 11 Aug 2021
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
  1 Comment
Anh Mai
Anh Mai on 11 Aug 2021
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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Wan Ji
Wan Ji on 11 Aug 2021
in line 3, do not use
domain=ones(nx,ny);
but use
domain=ones(ny,nx);
  1 Comment
Anh Mai
Anh Mai on 11 Aug 2021
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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