Find moving average with filter
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This is a class assignment. Teacher is assuming everyone has experience with filters and stuff. I definitely don't althought the rest of the class seems to.
We're supposed to use the "filter" command to find the running average of a vector containing integers from 1 to 10, ie y1 = 0.5*(x1+x2), y2= 0.5*(x2+x3) etc...
My approach would've been:
x = [1:1:10]
for j = 1:10 k = j+1 y(j) = 0.5*(x(j) + k) end
But they want us to use this filter function. I really can't interpret the documentation since I have no idea what a filter is even.
1 件のコメント
Matt J
2013 年 1 月 28 日
In my experience, it's a bad idea to take courses you lack prerequisites for.
回答 (4 件)
Daniel Shub
2013 年 1 月 28 日
The key part of the documentation is:
y(n) = b(1)*x(n) + b(2)*x(n-1) + ... + b(nb+1)*x(n-nb)
- a(2)*y(n-1) - ... - a(na+1)*y(n-na)
If you let all the a's be zero you get
y(n) = b(1)*x(n) + b(2)*x(n-1) + ... + b(nb+1)*x(n-nb)
If you then let b(1) = 0.5, and b(2) = 0.5, and zero otherwise
y(n) = 0.5*x(n) + 0.5*x(n-1) = 0.5*(x(n)+x(n-1))
Does that help?
0 件のコメント
Shashank Prasanna
2013 年 1 月 28 日
編集済み: Shashank Prasanna
2013 年 1 月 28 日
Appreciate your honesty. I recommend you go to wikipedia or your favorite signal processing book and take a deep loop at FIR filters.
Pay close attention to the block diagram. Although I will give you the code below, I want you to look at the block diagram and relate it to the "for" loop you wrote. Think about how the coefficients b0 b1 are the 1/2s and z_inverse delays the input in order to sum them. Think hard till it hits you and you will be like ah! and trust me you need this now for the rest of your course. Here is the block diagram from wiki:
and the code, go to the documentation of FILTER to see what each argument means.
data = 1:10;
filter([1 1]/2,1,data,1)
0 件のコメント
Matt Kindig
2013 年 1 月 28 日
編集済み: Matt Kindig
2013 年 1 月 28 日
Or even easier, go to the "Help" in Matlab, and search "moving average filter". The first or second link (the one entitled "Example: Moving Average Filter") will show you exactly how to do this using the 'filter' function.
1 件のコメント
Jan
2013 年 1 月 28 日
編集済み: Image Analyst
2013 年 1 月 28 日
Searching in the help is an answer for which I cannot vote enough.
Image Analyst
2013 年 1 月 28 日
Why not simply use conv()?
filteredSignal = conv(originalSignal, [.5, .5], 'valid');
1 件のコメント
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