# How can I calculate a centered moving average with window size 7?

5 views (last 30 days)
Kemal on 22 Jan 2013
Answered: nlm on 20 Feb 2020
Hello,
I want to calculate centered moving average of daily values using a 7-day window. That is I want to start with the 4th day being the first center and continue until the 1318 as the last center. And I want the filter to proceed successively from day 4, then 5, then 6, and so on until day 1318 as the center. I have 1321 daily values. I have NaN values in blocks and scattered throughout the data but would like to keep them. I've been given the below code but because I do not know programming, I can not make sense of how I can adapt this to get what I want done. My variable is called Imn_EVI2_d. Thank you for any help.
Daywind=3.5; % window size (days/2, i.e. half of the weekly window width)
Inc=1; %Time step increment (days)
binwid = (Daywind)/1321; %Specifies bin size
start = min(1); %Specifies timestamp when dataset starts Change
last = max(1321); %Specifies timestamp when dataset ends Change
bincenter = start+binwid:(Inc/1321):(last+1); %Specifies center of bin
binnum=length(bincenter); %Specifies how many bins for window size*
Imn_EVI2_d=m;
Imn_EVI2_avgmovall=[]; %Array that moving average will go into. Right now it is empty and 0x0.
Imn_EVI2_d=Imn_EVI2_d(1,:)'; %Change
%This is a for loop that takes the bins above and averages them and takes
%the average and saves it to EVIavgmovall
for i = 1:1:(binnum);
focusday = (1 >= (bincenter(i)-binwid) & (1321 <= (bincenter(i) + binwid)));
EVI_period = Imn_EVI2_d(focusday);
figure(1)
plot(DYear(focusday),Imn_EVI2_d(focusday),'.')
Imn_EVI2_movavg=nanmean(EVI_period);
Imn_EVI2_avgmovall=[Imn_EVI2_avgmovall Imn_EVI2_movavg];
end
Jan on 22 Jan 2013

Jan on 22 Jan 2013
d = [nan;2;3;nan;4;5;nan;6;nan;nan];
idx = isnan(d);
d(idx) = 0;
result = conv(d, ones(1,7), 'same') ./ conv(double(idx), ones(1,7), 'same');
Here not all sums over 7 neighboring elements are divided by the window width 7, but by the number of not NaNs.
Kemal on 23 Jan 2013
I see. What does the "double" command do? In the last row of the code, putting ~ before idx does the trick. Currently, it counts the number of NaNs.
Next step: How could I have the standard deviation calculated in the same fashion as the average calculation? Thank you!

Image Analyst on 22 Jan 2013
Assuming each element is the measurement for one day, can't you just do
movingAverage = conv(yourData, ones(1,7), 'same');
Image Analyst on 22 Jan 2013
Correct. Your answer does what I was thinking, and (trying to) describe.

Gary Kuepper on 24 Nov 2016
Why not use movmean function?
Image Analyst on 24 Nov 2016
Because when Kemal posted this almost 4 years ago, the movmean() function had not yet been introduced. Now, or actually since R2016a, you can use movmean().

nlm on 20 Feb 2020
Hi Kemal, did you find solution to your problem ? If so can you share ?

### Categories

Find more on Subplots in Help Center and File Exchange

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by