Sliding window to calculate intra-window difference

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Iram Shahzadi 2018-9-24

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/420411-sliding-window-to-calculate-intra-window-difference

评论： Adam Danz 2018-9-25

Capture algo 2.PNG

I have a matrix s=512*100*20 (with N=100). I want to implement sliding window of a width 2W+1 that is centered at position i to compute the intra-window difference s(i+w)-s(i-w) for every possible position. I have attached the algorithm. Anyone, please help me how to implement it in Matlab.

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Answer 1

Adam Danz 2018-9-24

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https://ww2.mathworks.cn/matlabcentral/answers/420411-sliding-window-to-calculate-intra-window-difference#answer_338032

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The formula in the attachment is written below. I don't know what your value W is and I don't now how your variable N comes into play.

% deltaW = nan(?,?);                %allocate your loop variable here after you know what its size should be.
for i = W : N-1-W
   deltaW(i) = s(i+W) - s(i-W);
end

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Iram Shahzadi 2018-9-24

Capture algo.PNG

Thank you @Adam for your reply. I think I have not described my problem well. Let me try again.

Actually, I have a signal 'g' 100*11, where 100 is length 'N' of the signal. My algorithm requires arranged data matrix stored in variable "data" so I have first sorted the signal 'g' by amplitude and arranged the "data" according to indexes of 'g'. Now I have to implement the sliding window on this arranged data to compute intra-window difference. I implemented it in same way as you suggested but I am getting error of 'invalid index' in tmp1(:,W-i,:). Can you please have a look at my code and algorithm again.

load s %size(s)=[100*11] load data; % size(data)=[512*100*20*11] [N, nt]=size(s); % N=100, nt=11 W=3; % Randomly selected

for ii=1:nt % I want loop to iterate 11 times tmp1=data(:,:,:,ii); % defining temporary virable for sorting [~,index]=sort(s(:,ii),'descend'); %sorting signal s tmp1=tmp1(:,index,:); % arrange my data accroding to signal s for i=W:N-1+W % applying window according to formula dff(:)= tmp1(:,i+W,:)-tmp1(:,W-i,:); end

end