nested for loop for moving average filter

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Jatin Arora
Jatin Arora 2012-11-29
Hello Everyone,
I want to implement nested for loop in MATLAB the first loop should run from 3 to n and inside this loop the second for loop should run for 1:5. My problem is I want to take averages of 5 numbers but a moving average. So i should start with average from elements 1 to 5 for first row, elements 2 to 6 for second row , elemets 3 to 7 for third row.
Please help me with this problem.
Thanks in Advance
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Jatin Arora
Jatin Arora 2012-11-29
编辑：Jatin Arora 2012-11-29
The problem was the length of initial array is not fixed and also the length of number of neighbouring points is not fixed. So I was not able to put a constant value. I was able to solve the problem
for i = 3:end
j1=i-No;
j2=i+No;
for j = j1:j2
PtsSum(i,:)=PtsSum(i,:)+PathPntIn(j,:);
end
end
Now I am stuck at a different thing. So will put a new question.
Image Analyst
Image Analyst 2012-11-29
You always have to decide what to do at the end when the window falls outside the signal. Looks like you want to just limit the window so that it never goes outside your signal. I think you need to do
for i = 2 : end-2 % not 3:end
where No is 2, which is the half width of a 5 element wide window.

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回答（2 个）

Jan
Jan 2012-11-29
No loops required in Matlab:
n = length(x);
mx = (x(1:n-4) + x(2:n-3) + x(3:n-2) + x(4:n-1) + x(5:n)) / 5;
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Daniel Shub
Daniel Shub 2012-11-29
I thought this would be faster than conv, but I was wrong. I wonder what the fastest method is for a moving average filter.

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Daniel Shub
Daniel Shub 2012-11-29
While you can do this with a loop, MATLAB has some highly optimized commands for filtering. The simpliest is probably conv.
First create some dummy date
N = 20;
x = randi(10, N, 1);
The M point moving average filter is
M = 5;
y = conv(x, ones(M, 1));

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