find nearest value on mesh grid under certain contour

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Katherine Zheng 2022-9-3

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https://ww2.mathworks.cn/matlabcentral/answers/1793915-find-nearest-value-on-mesh-grid-under-certain-contour

评论： Bruno Luong 2022-9-4

I have a surf matrix (colormap gray), a contour matrix (red). The magenta points are local minmum in red contours. I want to find the closest z value on the neigbhourhood contours. Is there any way to achieve this?

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Katherine Zheng 2022-9-4

The value is my priority concern then the distance.

Bruno Luong 2022-9-4

For each magenta point do you want to find the z value on the contour that enclosed the point? If the pointt is the locall minima, meaning that do you want to find the lowest Z along the contour?

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回答（1 个）

Chunru 2022-9-4

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1793915-find-nearest-value-on-mesh-grid-under-certain-contour#answer_1041415

在 MATLAB Online 中打开

load(websave("matlab.mat", "https://www.mathworks.com/matlabcentral/answers/uploaded_files/1116160/matlab.mat"))

% whos

surf(Xi2,Yi2,Zi2-max(Zi2(:)));

axis tight; title('m-min y-max')

colormap(gray); colorbar; %daspect([1 1 5]);

hold on

% red contour

surf(Xi2,Yi2,B2,'EdgeColor','r')

% peak and valley points

scatter3(Xi2(regmin),Yi2(regmin),Zi2(regmin),'mo','filled','sizedata',40)

scatter3(Xi2(regmax),Yi2(regmax),Zi2(regmax),'yo','filled','sizedata',40)

idxB2 = ~isnan(B2); % B2 has values of 0 and nans

% The values along the countour

Xc = Xi2(idxB2);

Yc = Yi2(idxB2);

Zc = Zi2(idxB2);

% These are values along the countour

[Xc Yc Zc]

ans = 727×3

1.3480 1.4440 0.0439 1.3480 1.4920 0.0357 1.3480 1.5160 0.0349 1.3480 1.6240 0.0122 1.3480 1.6480 0.0194 1.3480 1.6720 0.0230 1.3480 1.7560 0.0306 1.3480 1.7920 0.0192 1.3480 1.8160 0.0011 1.3480 1.8520 -0.0082