how to plot contour of 3D variable

Question

Amal MM 2024-8-17，21:49

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https://ww2.mathworks.cn/matlabcentral/answers/2146009-how-to-plot-contour-of-3d-variable

评论： Voss 2024-8-20，1:48

采纳的回答： Voss

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HI

I have issue with my data

I have salinity data with dimension (time,Lat,Lon) and I want to plot a filled 3-D contour

I want to plot salinity at specific

timestep 1:13

for example the size of variable

Lat=24*25;

Lon=24*25;

Salinty=744*24*25;

I am getting error becouse the X ,Y and Salinity had different size

I try for loop but it didn't worke

for i=1:12;
    Sal(i,:,:)=Salinity(i,:,:);
    figure
    contourf(X,Y,Sal(i,:,:);
    
end

Can someone help?

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Answer 1

Voss 2024-8-18，23:46

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编辑：Voss 2024-8-18，23:47

在 MATLAB Online 中打开

Example data:

Salinity = rand(744,24,25);
[Lat,Lon] = ndgrid(1:24,1:25);
whos Lat Lon Salinity
  Name            Size                 Bytes  Class     Attributes

  Lat            24x25                  4800  double              
  Lon            24x25                  4800  double              
  Salinity      744x24x25            3571200  double              

If you want a sequence of filled contours:

tmp = permute(Salinity,[2 3 1]);

whos tmp

Name Size Bytes Class Attributes tmp 24x25x744 3571200 double

for ii = 1:3 % first 3 times only

figure

contourf(Lon,Lat,tmp(:,:,ii));

end

Your code didn't work because Sal(i,:,:) is of size 1-by-24-by-25 but contourf expected a matrix of size 24-by-25.

In my suggested code, permute rearranges the dimensions of Salinity to make tmp, which is of size 24-by-25-by-744, so that each tmp(:,:,ii) is a matrix of size 24-by-25.

https://www.mathworks.com/help/matlab/ref/permute.html

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Amal MM 2024-8-20，1:17

Thank you I greatly appreciate it work

Voss 2024-8-20，1:48

You're welcome!

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Answer 2

Walter Roberson 2024-8-17，22:58

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In order to do 3D contours, you need to call isosurface . You would call it several times, once for each contour level.

However, filling the 3D contours is a bit of a problem.

I have to ask whether filling the contours is really necessary, as opposed to just drawing their surfaces? Since their entire surface would be drawn, the only visual difference between surface-only and surface-and-fill would be the visual effect of transparency -- showing darker locations where the view happens to strike more of the volume. That kind of visual hint is not without merits, but is it worth the trouble?