How do I maintain my array size (or dimensions) when I run it through a nested for loop?

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NA 2020-9-1

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评论： NA 2020-9-1

Hi All,

I have an array, 'data' (5x16x2), that I have shifted to the left (by 1 column) and zero-padded the right accordingly. However, when I run my variable through a nested for loop, my 3d array gets transformed to 2d (5x32). I'm facing some trouble trying to figure out how to maintain my array size as I run it through the nested for loop. I essentially want my 'dataShift' varible to be the same size as my 'data' variable (5x16x2).

My code looks like this:

%dummy data
for ii = 1:2
    for i=1:16
        data(:,i,ii)=i(:,:);
    end
end
%constant variables
sink = 8;
layerIV = 7;
shift = abs(layerIV - sink);
%shift data
for ii = 1:2
  for ch = 1:16
    if sink > layerIV
      dataShift = [data(:, shift+1:end), zeros(size(data,1),shift)];
    end
  end 
end 

I thought that perhaps the following might work:

dataShift(:,ch,ii) = [data(:, shift+1:end), zeros(size(data,1),shift)];

But I get the following error: "Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 1-by-32."

Would really appreciate any help.

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Answer 1

Dana 2020-9-1

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You have 3-D arrays but are only using 2-D indexing (e.g., data(:, shift+1:end) only has two indices, even though data is a 3-D array). That's going to give you unexpected results. Also, your dummy data vector doesn't have 5 rows, just 1, which I'm assuming is a mistake.

I'm not entirely clear on exactly what you're after here, but does this give the desired result?

data = repmat(1:16,5,1,2); % better way to create your dummy data
%constant variables
sink = 8;
layerIV = 7;
shift = abs(layerIV - sink);
dataShift = [data(:,shift+1:end,:),zeros(size(data,1),shift,size(data,3))];