Convolution without any Built-in Commands
6 ビュー (過去 30 日間)
古いコメントを表示
Hey guys, I'm trying to learn how convolution works without any built in fft or
conv commands, and I'm not quite sure how to write it. I'm starting at index 1 in
this case, so y(n) =(x*h)(n)= sum from 1 to infinity of (x(k)h(n-k+1)), and
trying to use just arrays and no loops, while also creating a stem plot. The lack
of a for loop is giving me the most trouble, any suggestions?
3 件のコメント
回答 (2 件)
Matt J
2012 年 11 月 24 日
TOEPLITZ isn't a built-in command. You could use that to implement convolution, e.g.,
>> A=toeplitz([2 3, zeros(1,8)],[2 1 0 0 0 0 0 0 0 0 ]), b=rand(10,1);
A =
2 1 0 0 0 0 0 0 0 0
3 2 1 0 0 0 0 0 0 0
0 3 2 1 0 0 0 0 0 0
0 0 3 2 1 0 0 0 0 0
0 0 0 3 2 1 0 0 0 0
0 0 0 0 3 2 1 0 0 0
0 0 0 0 0 3 2 1 0 0
0 0 0 0 0 0 3 2 1 0
0 0 0 0 0 0 0 3 2 1
0 0 0 0 0 0 0 0 3 2
>> A*b-conv(b,1:3,'same')
ans =
1.0e-15 *
0
0.4441
0.8882
0
0
0.8882
-0.4441
0
0
0
3 件のコメント
Matt J
2012 年 11 月 25 日
Why don't you test it against the output of conv() to see if you get the same results?
Image Analyst
2012 年 11 月 25 日
I think you mean x(n) ** h(n), which is the usual textbook notation for convolution, rather than (x*h)(n). The code it's not exactly the way I'd do it (padding with zeros, etc.) but it's easy enough to test, like Matt suggested. I would use the double for loop though.
Jan
2012 年 11 月 25 日
Even CONV is not a built-in function. But it calls conv2(), which is built-in now.
conv(a,b) can be calculated using:
c = filter(a, 1, b);
when the shorter of the inputs is padded by zeros. And filter() can by run as M-file also, see http://www.mathworks.com/matlabcentral/answers/9900#answer_13623. And considering the special inputs, this code can be improved.
0 件のコメント
参考
カテゴリ
Help Center および File Exchange で Loops and Conditional Statements についてさらに検索
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!