Sliding window: array gets smaller
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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!
7 个评论
KALYAN ACHARJYA
2022-10-28
Have you checked imfilter() funtion to slide the window (effiecint way)?
Adam Danz
2022-10-28
The number of elements in your smoothed array size should only differ by "windowLength". You can shorten the length of your time vector by the same number of units for plotting. Smoothed data at time t(n) represents data smoothed between the interval of t0(n) and t0(n)+windowLength-1.
Milena
2022-10-29
Rik
2022-10-30
What exactly do you mean? Were the values you got unexpected? Or did you run into errors?
Milena
2022-11-1
Rik
2022-11-1
And how did you determine that this was due to an incorrect implementation and not inherent to your data?
回答（1 个）
Image Analyst
2022-10-28
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.
3 个评论
Are you sure about that? AFAIK, imfilter() handles all its edge treatment by padding. There are options for how the padding is generated and the extent of the returned array, but I don't recall anything about kernel truncation options. Same goes for medfilt2(), stdfilt(), etc.
EDIT: maybe you mean movmean(), movmedian(), etc. Those have truncation options.
Image Analyst
2022-10-28
@DGM, you're right.
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