reduce the length by summing the bins

Question

Junaid 2012-6-24

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/41917-reduce-the-length-by-summing-the-bins

评论： Tamara del Águila 2021-5-23

dear all,

Let say I have matrix of Histograms, where each column is one histogram vector. What I want is to sum two bins each other, i.e., first bin + second bin, Third bin + forth bin.

Let say

output should be

B =
 [ 5    7  9
   17   19  21 ]

Is it possible without using loops.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Walter Roberson 2012-6-24

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/41917-reduce-the-length-by-summing-the-bins#answer_51614

在 MATLAB Online 中打开

B = A(1:2:end, :) + A(2:2:end,:);

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Junaid 2012-6-24

Thank you.

请先登录，再进行评论。

Answer 2

Jan 2012-6-24

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/41917-reduce-the-length-by-summing-the-bins#answer_51635

在 MATLAB Online 中打开

Faster for large arrays, because it does not create temporary arrays, e.g. 3 times faster for [1e5 x 3] in Matlab 2009a/64/Win:

B = reshape(sum(reshape(A, 2, 2, 3)), 2, 3);

[EDITED] General approach:

newLen = size(A, 1) / 2;
B = reshape(sum(reshape(A, 2, newLen, 3)), newLen, 3);

5 个评论
显示 3更早的评论隐藏 3更早的评论

Tamara del Águila 2021-5-21

... and how could I possibly downsample an array binning the data? With resample is not possible because it calculate averages, so I was wondering if it would be possible to do it with something like this answer, so that the matrix can be resize (let's say, to the half or less) without loosing the counts.

Tamara del Águila 2021-5-23

About what I further commented on the topic, In any case anyone is interested, has the same problem, or would like to share its knowledge about the specific issue, I have posted a formal question, because I am stuck with it...

https://nl.mathworks.com/matlabcentral/answers/837388-how-to-bin-data-from-a-matrix-2d-array?s_tid=srchtitle

thanks!

请先登录，再进行评论。