How to calculate mean in moving cubic volume?

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SojM 2020-7-25

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https://ww2.mathworks.cn/matlabcentral/answers/570409-how-to-calculate-mean-in-moving-cubic-volume

回答： Amy Van Wey Lovatt 2022-9-11

I have a stack of 2D images in 3D array format 100x100x500. Now I want to select a small cubic volume of 1x1x1 at center of the stack and increase this cubic volume step by step till I reach the array size, calculating mean at each stage. I know I need to use mat2cell and mean function. How can be done in corect for loop?

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Answer 1

Matt J 2020-7-25

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https://ww2.mathworks.cn/matlabcentral/answers/570409-how-to-calculate-mean-in-moving-cubic-volume#answer_470761

编辑：Matt J 2020-7-25

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I know I need to use mat2cell and mean function.

I don't think you do. Let's call your 3D volume, V:

[ci,cj,ck]=deal(51,51,251); %center coordinate ?
[I,J,K]=ndgrid(abs((1:100)-ci),abs((1:100)-cj),abs((1:500)-ck));
L=max(max(I,J),K)+1; %label matrix
stats = regionprops3(L,V,'MeanIntensity','Volume');
cumVolumes = cumsum(stats.Volume);
cumIntensities = cumsum(stats.Volume.*stats.MeanIntensity);
result = cumIntensities ./cumVolumes

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Matt J 2020-8-2

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Something like this?

clear S
S(400)=struct('cumVolumes',[],'cumIntensities',[],'result',[]); %pre-allocate
for i = 1:400
    
    [ci,cj,ck]=deal(51,51,50+i); %center coordinate
    [I,J,K]= ndgrid(abs((1:100)-ci),abs((1:100)-cj),abs((i:100+i)-ck)); % Z remain 100 but changes with center
    L = max(max(I,J),K)+1; %label matrix
    stats = regionprops3(L,V(:,:[i:100+i]),'MeanIntensity','Volume');
    
    
    S(i).cumVolumes = cumsum(stats.Volume);
    S(i).cumIntensities = cumsum(stats.Volume.*stats.MeanIntensity);
    S(i).result = cumIntensities ./cumVolumes
end 

SojM 2020-8-2

编辑：SojM 2020-8-2

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Thanks Matt. Yes, I was looking for somethign like that. That was very useful. Your code gave me error that "Undefined function or variable 'cumIntensities' ". I needed to define them before using as struct fields. It is working perfectly now. Following is the modified version of your code:

clear S
S(400)=struct('cumVolumes',[],'cumIntensities',[],'result',[]); %pre-allocate
for i = 1:400
    
    [ci,cj,ck]=deal(51,51,50+i); %center coordinate
    [I,J,K]= ndgrid(abs((1:100)-ci),abs((1:100)-cj),abs((i:100+i)-ck)); % Z remain 100 but changes with center
    L = max(max(I,J),K)+1; %label matrix
    stats = regionprops3(L,V(:,:,[i:100+i]),'MeanIntensity','Volume');
    
    cumVolumes = cumsum(stats.Volume);
    cumIntensities = cumsum(stats.Volume.*stats.MeanIntensity);
    result = cumIntensities ./cumVolumes;
    
    S(i).cumVolumes = cumVolumes;
    S(i).cumIntensities = cumIntensities;
    S(i).result = result;
end 