# Mean of certain elements within a matrix

조회 수: 52(최근 30일)
Malik Khan 2019년 12월 11일
댓글: RAMPUNIT KUMAR 2021년 9월 1일
I have a matrix which is a 372x6. Rather than find a mean for a specific row or a specific column, I want to find the mean of elements that lay in different rows as
Although the elements are from different rows, I have a pattern for the order in which they are to be taken. The last 2 elements (column 5 and 6) is to be averaged with the second third and fourth of the following row. The mean then needs to be found for each line. To make this easier to visualise I have written out a matrix for which we need to find 2 means. We need one mean to be of (e f h i j) and the other (k l m n o). For my case however I need to do this 371 times as we have 372 lines (obviously we can’t find mean for the first row).
(a b c d e f)
(g h i j k l)
(l m n o p q)
##### 댓글 수: 1표시숨기기 없음
RAMPUNIT KUMAR 2021년 9월 1일
I too have a doubt, like for matrix
(a b c d e f g h I j k l m n o p q r)
I need to find the mean of a,b then c,d then e,f then g,h and so on upto last element. How could we do that if size is big enough.

댓글을 달려면 로그인하십시오.

### 채택된 답변

Stijn Haenen 2019년 12월 11일
I think this will work:
for i=1:371
Mean_i(i)=mean([matrix(i,5:6),matrix(i+1,2:4)]);
end

댓글을 달려면 로그인하십시오.

### 추가 답변(2개)

Bandar 2019년 12월 11일
편집: Bandar 2019년 12월 11일
A=[1 2 3 4 5 6; 7 8 9 10 11 12;13 14 15 16 16 18;19 20 21 22 23 24]
[row,~]=size(A);
for i=1:row-1
c = A(i,[5 6]);
r = A(i+1,[2 3 4]);
B = [c r]
mean(B)
end
##### 댓글 수: 1표시숨기기 없음
RAMPUNIT KUMAR 2021년 9월 1일
RAMPUNIT KUMAR less than a minute ago ⋮ I too have a doubt, like for matrix (a b c d e f g h I j k l m n o p q r) I need to find the mean of a,b then c,d then e,f then g,h and so on upto last element. How could we do that if size is big enough.

댓글을 달려면 로그인하십시오.

Andrei Bobrov 2019년 12월 11일
편집: Andrei Bobrov 2019년 12월 11일
Here A - your array (m x 6)
[m,n] = size(A);
i = repmat((0:m-1)',1,n-1);
i(:,end-1:end) = circshift(i(:,end-1:end),-1);
i = [zeros(m,1),i];
lo = i ~= 0;
out = accumarray(i(lo),A(lo),[],@mean);
or
[m,n] = size(A);
i = [zeros(m,1),reshape(circshift(repelem(0:m-1,n-1),-2),n-1,[])'];
out = accumarray(i(i>0),A(i>0),[],@mean);
##### 댓글 수: 1표시숨기기 없음
RAMPUNIT KUMAR 2021년 9월 1일
RAMPUNIT KUMAR less than a minute ago ⋮ I too have a doubt, like for matrix (a b c d e f g h I j k l m n o p q r) I need to find the mean of a,b then c,d then e,f then g,h and so on upto last element. How could we do that if size is big enough.

댓글을 달려면 로그인하십시오.

R2019b

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!