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Calculate moving average manually

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FS
FS on 10 Oct 2020
Edited: FS on 7 Nov 2020
This question was flagged by Image Analyst
y[n] = 1/M Σx[n − k]
lower limit k= 0 upper limit M −1
Write a function that performs the moving average for any non-zero and positive order M. Make sure to add M-1 zeros at the beginning of the data so that your output data will be the same length as your input data.
I have this so far:
function [movaverage] = movaverage(M)
M=zeros(1,length(M));
for i=1:length(t)-M
y1(i)=(1/M)*sum(i:i+M-1);
end
y=[zeros(1,M) y1];
figure
subplot(211)
plot(t,x,'b')
ylabel('Signal')
axis([0 3 0 30])
subplot(212)
plot(t,y,'r')
ylabel('Moving avg')
xlabel('Time (s)')
axis([0 3 0 inf])

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Image Analyst
Image Analyst on 11 Oct 2020
You need an outer loop over n but not like you have. You need to use M, not k
for n=1:length(x)-(2*M+1) % M is the window width
Then the inner loop needs to be over k where k goes from 0 to M-1, just like your instructions said. Then you need to sum y and divide by M, again, like the instructions said, not like what you did which was to divide by (2*k+1). If you sum a sequence of M elements in y, then divide by M, you get the average value in that segment of y.
Rik
Rik on 7 Nov 2020
If you want to avoid being caught cheating, you should not post your question to a website that is being cached by Google.
Moving average without using movmean() or conv()
Write a function that performs the moving average of any 1-dimensional input data for any non-zero and positive order M. Make sure to add M-1 zeros at the beginning of the data so that your output data will be the same length as your input data. You must not use built in functions like movmean() or conv().
y[n] = 1/M Σx[n − k]
lower limit k= 0 upper limit M −1
I have this so far:
function [movaverage] = movaverage(M)
M=zeros(1,length(M));
for i=1:length(t)-M
y1(i)=(1/M)*sum(i:i+M-1);
end
y=[zeros(1,M) y1];
figure
subplot(211)
plot(t,x,'b')
ylabel('Signal')
axis([0 3 0 30])
subplot(212)
plot(t,y,'r')
ylabel('Moving avg')
xlabel('Time (s)')
axis([0 3 0 inf])

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Accepted Answer

Image Analyst
Image Analyst on 10 Oct 2020
I'm attaching a fully manual 2-D convolution. It should be easy for you to adapt it to 1-D

  1 Comment

Image Analyst
Image Analyst on 20 Oct 2020
I see you're editing the original question to follow my advice in my comment above:
"
You need an outer loop over n but not like you have. You need to use M, not k
for n=1:length(x)-(2*M+1) % M is the window width
Then the inner loop needs to be over k where k goes from 0 to M-1, just like your instructions said. Then you need to sum y and divide by M, again, like the instructions said, not like what you did which was to divide by (2*k+1). If you sum a sequence of M elements in y, then divide by M, you get the average value in that segment of y.
"
So, did that help you? Are we done yet and you can Accept this answer? Or do you still have questions?

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