Extract and average from matrix

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Joseff Saunders
Joseff Saunders 2018-12-4
编辑： Image Analyst 2018-12-4
Hello all, Im trying to extract every 7 rows of a matrix and average them (mean). As an example:
4.20
4.10
4.10
4
3.90
3.80
NaN
3.80
3.90
3.90
3.70
3.60
3.60
3.40
3.40
3.30
3.30
3.30
3.30
3.10
3.10
What code would i need to take the first 7 rows and average them, and to continually do this for the matrix i.e. average of rows 1:7 8:14 15:21
Thanks in advance.

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采纳的回答

Bob Thompson
Bob Thompson 2018-12-4
The lowest difficulty way of doing this, that I can think of, is to use a for loop.
for i = 1:length(data)/7;
ave(i) = mean(data(7*(i-1)+1:i*7));
end
If you're looking for a non-loop method you might try using reshape first, and then average each column.
data2 = reshape(data,7,[]);
ave = mean(data2);
  2 个评论
Image Analyst
Image Analyst 2018-12-4
编辑：Image Analyst 2018-12-4
The second method (same as my answer below) is clever if you've never seen it before.
We see this question (and the answer) all the time - I guess I should add it to the FAQ.
EDIT: OK, I've added it to the FAQ: How do I compute the mean of a vector in blocks?

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更多回答（1 个）

Image Analyst
Image Analyst 2018-12-4
Try reshape()
vec = (1 : 70)' % Sample data
m2d = reshape(vec, 7, [])
means7 = mean(m2d, 1)

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