sum every 2 pages at a time in 3D matrix

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AJ
AJ 2018-7-13
编辑： James Tursa 2018-7-13
I'm trying to sum every 2 pages at a time in 3D data.
for example, suppose I have 3x2x5 double data like this:
data = ones(3,2,5);
after I sum every 2 pages then I can get 3x2x3 double data like this:
data(:,:,1) =
2 2
2 2
2 2
data(:,:,2) =
2 2
2 2
2 2
data(:,:,3) =
1 1
1 1
1 1
I'm not sure you can understand what I'm saying..please leave comment if you need more explanation.
The JPG file I attached(pic.jpg) might help you understand.
Many thanks to all

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采纳的回答

James Tursa
James Tursa 2018-7-13
编辑：James Tursa 2018-7-13
Another way:
p = 2; % number of pages at a time to sum
datas = data;
m = mod(size(datas,3),p);
if( m )
datas(end,end,end+p-m) = 0; % pad if needed
end
datas = reshape(datas,size(datas,1),size(datas,2),p,size(datas,3)/p);
result = sum(datas,3);
result = reshape(result,size(data,1),size(data,2),[]);

更多回答（1 个）

Rik
Rik 2018-7-13
The code below isn't the most efficient for your example, but will work in more complicated situations.
data = ones(3,2,5);
k=2;%number of last dimension to be summed
d=numel(size(data));sumdata_part=cell(k,1);
for k2=1:k
% This part doesn't support other dimensional examples,
% but that can be done as well if you need it to.
sumdata_part{k2}=data(:,:,k2:k:end);
end
%ensure same sizes
temp=zeros(size(sumdata_part{1}));
temp(1:numel(sumdata_part{end}))=sumdata_part{end};
sumdata_part{end}=temp;
%concatenate in a new direction and sum over that dimension
outcome=sum(cat(d+1,sumdata_part{:}),d+1)

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