MATLAB Answers

Get max or min value from a mesh plot interactively?

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Juan Vences
Juan Vences on 2 Aug 2021
Commented: Juan Vences on 4 Aug 2021
Hello everybody,
It's been a while since last time I used Matlab (lol), and any help would be highly appreciated :)
Currently I'm figuring out ways to get max or min values from a figure like the one attached in this post
Ideally it would be great to get the max and min with an interactive "selection window" (example is from a screenshot from Paint with the "desired concept").
The figure is a "mesh surface" with "colormap(jet)" and color bar as shown in the screenshot (attached).
Any ideas guys?
Many thanks!
  1 Comment
Juan Vences
Juan Vences on 2 Aug 2021
Forgot to mention this detail:
Get "x", "y" corresponding to that max or min "z" value

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Accepted Answer

Dave B
Dave B on 2 Aug 2021
Without implementing something to draw the rectangle and display the result, you can get this with an extra step or two using brushing:
mesh(peaks, 'FaceColor', 'flat')
brush %or click the icon that looks like a paintbrush in the upper right corner of the axes
click and drag to select a region, it will show up as red
right click and choose 'Export brushed'
Choose a variable name or use the default, now the data is available in the command window
Juan Vences
Juan Vences on 4 Aug 2021
Thank you @Dave B
Yes, this is totally an index stuff and shouldn't be a big deal for Matlab... is more a big deal for me... '^_^
Thank you for your answer

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More Answers (1)

Image Analyst
Image Analyst on 2 Aug 2021
Edited: Image Analyst on 2 Aug 2021
Since it looks like an image, I believe you can use drawrectangle() and then just use min and max on the sub-image you get by indexing.
rgbImage = imread('cameraman.tif');
subplot(1, 2, 1);
imshow(rgbImage, 'Colormap', hsv(256));
g = gcf;
g.WindowState = 'maximized';
axis on;
uiwait(helpdlg('Drag out a rectangle'));
roi = drawrectangle()
p = round(roi.Position)
subImage = imcrop(rgbImage, p);
subplot(1, 2, 2);
axis on;
meanValue = mean2(subImage)
minValue = min(subImage(:))
maxValue = max(subImage(:))
message = sprintf('The Mean Gray Level is %f', meanValue);
title(message, 'FontSize', 20);
  1 Comment
Juan Vences
Juan Vences on 4 Aug 2021
Thank you so much @Image Analyst !
I think this one is real nice and elegant option, it is so good that I am not at its level '^_^
Hope to use one day
However, it is correct that my doubt is so simply that doesn't not deserve such a high quality answer. But I highty appreciate your time!
Thank you

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