Non-Overlapping Moving Sum

Consider any matrix, say Rain=(1:10)'. I want to compute a non-overlapping moving sum with two element.
Rain=1,2,3,4,5,6,7,8,9,10
Compute=1+2,3+4,5+6,7+8,9+10
With traditional movsum command, the moving sum is overlapping elements. I want to evaluate non-overlapping moving sum. Any in-built function? I have tried with loops and all those, it works but in-built function would be fast to compute.

 采纳的回答

Try this —
Rain = [1,2,3,4,5,6,7,8,9,10];
rRain = reshape(Rain, 2, [])
rRain = 2×5
1 3 5 7 9 2 4 6 8 10
sumRain = sum(rRain)
sumRain = 1×5
3 7 11 15 19
These could be combined into one line, however I kept them separate to demonstrate how it works.
.

6 个评论

Actually my matrix has size 135*129*118. I wanted to accomplish this non-overlapping 2 sum so that my final matrix is 135*129*59. I tried using reshape, but may be i did some mistake the resultant matrix wasn't the one i wanted, could you provide some hint for 3-d matrix?
It always helps to have the actual problem in the beginning.
Every combination of permute, reshape and sum that I experimented with failed to provide the desired result.
.
Star's right - avoids wasting time if we know the full situation in advance. However he showed you a nice trick that will come in useful. It's also in the FAQ:
You can download sepblockfun, which generalizes the technique Star Strider has shown to higher dimensions.
A=rand(135,129,118);
B=sepblockfun(A,[1,1,2],'sum');
whos A B
Name Size Bytes Class Attributes A 135x129x118 16439760 double B 135x129x59 8219880 double
@Matt J — Thank you! I didn’t think to look in FEX.
This worked thanks @Matt J and everyone

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更多回答(1 个)

Image Analyst
Image Analyst 2021-6-27

0 个投票

Since you have an image, you can do it with blockproc. However it only works with 2-D arrays so you'll have to do it once on each slice, then again along the z direction. I'm attaching some blockproc demos. I haven't done it with a 3-D image so you're on your own but I'm pretty sure it can be done.

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