End Points on movmean don't look right
7 ビュー (過去 30 日間)
古いコメントを表示
If you run the simple code (see end of post) you are taking the sliding window filter using matlab "movmean". Per the description:
"The window size is automatically truncated at the endpoints when there are not enough elements to fill the window. When the window is truncated, the average is taken over only the elements that fill the window. M is the same size as A."
If I read this correctly-for element 1 of the dataset, only element 1 "fills the window". Thus the average of A(1) is just A(1)/1 =1. Looking at my plot I do not see this--it appears as thought the first element is wrong--instead of 1, movmean returns 1.5.
What did I miss here?
Thanks--Fritz
========================================
for i=1: 10
A(i)=i;
end
for i=11: 20
A(i)=20-i;
end
plot(A,'b','LineWidth',2);
M=movmean(A,3)
hold on;
plot(M,'k','LineWidth',2);
fprintf("A(1)=%f\n",A(1)) ;
fprintf("M(1)=%f\n",M(1)) ;
fclose all;
1 件のコメント
採用された回答
Matt J
2021 年 10 月 2 日
編集済み: Matt J
2021 年 10 月 2 日
If I read this correctly-for element 1 of the dataset, only element 1 "fills the window".
No, the length 3 window is centered on element 1, so element 2 will also be in the window. The value of 1.5 is the average of [1,2]. If you don't want the current element to lie at the right hand edge fo the window, you can do
movmean(A,[2,0])
0 件のコメント
その他の回答 (2 件)
Image Analyst
2021 年 10 月 2 日
When the center of your 3-element window is over element 1 of A, which is
A =
1 2 3 4 5 6 7 8 9 10 9 8 7 6 5 4 3 2 1 0
the values 1 and 2 are inside the window.
The window does not travel so far that the center of the window is off the left side of A and only the tail overlaps the first element of A. If it did, then the output matrix would be larger than A.
So, the average of 1 and 2 is 1.5, like it is for M.
0 件のコメント
Fritz Sonnichsen
2021 年 10 月 2 日
1 件のコメント
Matt J
2021 年 10 月 2 日
Glad you worked it out, but please Accept-click one of the answers, so that Mathworks has a record that a resolution was reached.
参考
カテゴリ
Help Center および File Exchange で Matrices and Arrays 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!