How to average more than 50 3D matrices using nanmean

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raheem mian 2019-11-14

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编辑： Matt J 2019-11-15

Hi, I am trying to average a lot of 3D matrices using NaNmean. I have tried using cat but my 3D matrices are huge (351x400x400) which is using a lot of memory. Is there a better way to do this ?

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Adam Danz 2019-11-14

编辑：Adam Danz 2019-11-14

Hmmmm... concatenating 50 arrays that each have more than 56 million elements isn't going to happen.

Off the bat I can think of a couple ideas.

1) Using 2 loops, you can loop through each file and partially load each 351 x 400 slice so you have 50 of those matricies which would make ~7m data points. If that's still too large you could partially load in each 351x1 column. Then you can do element-wise averaging and store the values as you proceed through the loops. That would involve 50 x 400 loops which isn't a big deal.

2) you can reorganize your data as tall arrays which are designed for large amounts of data.

raheem mian 2019-11-14

This idea is perfect, Thank you!

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采纳的回答

Matt J 2019-11-14

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https://ww2.mathworks.cn/matlabcentral/answers/491158-how-to-average-more-than-50-3d-matrices-using-nanmean#answer_401565

编辑：Matt J 2019-11-15

在 MATLAB Online 中打开

Here's what I would do, I suppose. It assumes each of your .mat files stores the volume under the name 'a'.

Summation=0;
NCounter=0;
files=dir(fullfile('yourFolder','*.mat'));
for i=1:numel(files)
    
   S=load(fullfile('yourFolder',files(i).name)); 
   
   map=isnan(S.a);
   
   S.a(map)=0;
   
   Summation = Summation + S.a;
   NCounter  = NCounter + (~map);
    
end
result = Summation./Ncounter;