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How to find peaks in 3d mesh?
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OldCar
el 6 de Abr. de 2016
Respondida: Poison Idea fan
el 1 de Mayo de 2024
Hi, I have a mesh made from data ([Y,X] matrix and Z values) and I would like to find the peaks and report their position. How can I do it?
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Mike Garrity
el 6 de Abr. de 2016
Editada: Mike Garrity
el 6 de Abr. de 2016
If your X & Y are monotone, and you have the Image Processing Toolbox, then the imregionalmax function is pretty robust. It handles all of the special cases like flat regions.
[x,y] = meshgrid(linspace(-3,3,10));
z = 10*ones(10,10);
z(2:4,2:4) = 22;
z(6:8,6:8) = 33;
z(2,7) = 44;
z(3,8) = 45;
z(4,9) = 44
surf(x,y,z,'FaceColor','interp')
ix = find(imregionalmax(z));
hold on
plot3(x(ix),y(ix),z(ix),'r*','MarkerSize',24)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/174012/image.png)
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Chibuzo Nnonyelu
el 13 de Dic. de 2018
You need to use the meshed X and Y. As in, fetched your ix indices from the meshed X and Y.
Más respuestas (3)
Cristian Alistarh
el 17 de Jun. de 2020
Editada: Cristian Alistarh
el 17 de Jun. de 2020
I think you got this error:
Index exceeds the number of array elements
As stated above, you need to use the meshed X and Y.
Digging further into this, the indicies of the output of the imregionalmax function is given in linear array indicies and not 2D (row, columns) as one would normally expect. I had the same problem and another way to solve this is to use the convert linear indices to subscripts function ind2sub
ix = find(imregionalmax(z));
[a,b] = ind2sub(size(z),ix);
plot3(x_init(a),y_init(b),z(a,b),'r*','MarkerSize',24)
I am not sure if it will give you 100% what you are looking for, but explains the previous behaviour and another way on how to fix it.
Poison Idea fan
el 1 de Mayo de 2024
Matlab 2024a has a new function islocalmax2 that can find peaks for 3D surface.
https://www.mathworks.com/help/matlab/ref/islocalmax2.html#mw_ecf7d164-82f0-4175-b939-b61c0f9c7f29
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