Sliding window in a matrix

Question

Diana 2015-11-10

0
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https://ww2.mathworks.cn/matlabcentral/answers/254119-sliding-window-in-a-matrix

评论： Joseph Cheng 2015-11-12

Hello Guys, I have this code that runs through a matrix of (6000,3). My code runs each column and then each element in the column (rows). If the values of the column are bigger than the threshold it returns one and if they are smaller returns 0. But it is to sensitive for my data, I want to use a window that runs through 500 elements in the column and if half or more of them are bigger than the threshold give one to that entire window. How do I do this? So far its running each element at the time. This is the code:

for i=1:1:3;                        %runns trhough the matrix
   SD=std(E(:,i))
   thresh=SD
   for ii=1:1:length(E(:,i));    %runs trhough every element
      if E(ii,i) > thresh;
          detect(ii,i)=1;
      else
          detect(ii,i)=0;
      end
  end 
end

Thanks!

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Answer 1

Joseph Cheng 2015-11-10

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https://ww2.mathworks.cn/matlabcentral/answers/254119-sliding-window-in-a-matrix#answer_199272

在 MATLAB Online 中打开

you can perform what you're doing a bit simpler.

E = randi(100,6000,3); %my generation of dummy data
windowL =500;
thresh= 50;
for ind = 1:length(E(:,1))-windowL+1 % set the end such that you don't index more than the length of the array E.
    Window = E(ind:ind+windowL-1); %pulled out section of E to be used 
    tWindow = Window>thresh; %  threshold the window you'll get a 500x3 logical array
    stWindow = sum(tWindow); % then take the sum to count how many are over the threshold per column (you'll end up with a 1x3 matrix of how many are over the threshold.
    tstwindow = stWindow>windowL/2; % then you can threshold again to see which ones have a majority over the threshold.
    detect(ind,:) = ttwindow; %then set your detected array based on the last calculation.
end