Sliding window: array gets smaller

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Milena 2022-10-28

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https://ww2.mathworks.cn/matlabcentral/answers/1838253-sliding-window-array-gets-smaller

评论： Rik 2022-11-1

I am currently working on implementing a sliding window into my code. This is is what i have got so far:

windowLength = 10;
        for i = 1:length(green)-windowLength
            greenDC(i) = mean(green(i:i+windowLength-1));
            redDC(i) = mean(red(i:i+windowLength-1));
            greenAC(i) = std(green(i:i+windowLength-1));
            redAC(i) = std(red(i:i+windowLength-1));
            
            %other codes
        end 

My problem is now, that i want to plot my results i get later in the code over the time axis t. But after my sliding window the arrays get smaller by 10 and now my time array is to big for the plotting to work.

Does anybody know how to solve this problem? Or is my sliding window completly wrong?

I already tried to interpolate the time, but its not working.

thanks in advance!

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Milena 2022-11-1

The error I calculated got bigger with movmean than without

Rik 2022-11-1

And how did you determine that this was due to an incorrect implementation and not inherent to your data?

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回答（1 个）

Image Analyst 2022-10-28

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https://ww2.mathworks.cn/matlabcentral/answers/1838253-sliding-window-array-gets-smaller#answer_1086383

在 MATLAB Online 中打开

If you want to shrink the window, try this (untested)

windowLength = 10;
for i = 1:length(green)
    index2 = min([length(green), i + windowLength - 1]);
    greenDC(i) = mean(green(i:index2));
    redDC(i) = mean(red(i:index2));
    greenAC(i) = std(green(i:index2));
    redAC(i) = std(red(i:index2));    
    %other codes
end 

You know, imfilter has edge effect options, including shrinking window as it approached the edge of the signal or image.

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Image Analyst 2022-10-28

@DGM, you're right.

Rik 2022-10-29

编辑：Rik 2022-10-30

I believe the default behavior of this or a related function changed around R2017b. When I get home I will look up what function exactly and what the change was.

Edit: turns out it was R2017a, where imclose pads the image by half the size of the SE.

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