Sum columns of matrix

5 views (last 30 days)
Esegboria Osarhemen
Esegboria Osarhemen on 10 Feb 2019
Edited: Stephen23 on 10 Feb 2019
If I have a 3x6 matrix like this
1 5 2 4 3 2
2 3 1 4 4 1
4 5 2 2 3 1
how can i sum(without a loop) columns 1:2, 3:4, 5:6, to form a new 3x3 matrix?
And if have a 3x12 like this
2 1 2 1 1 5 5 4 4 2 4 5
3 5 1 3 1 2 5 3 3 4 5 4
2 4 2 1 5 5 4 3 2 2 1 5
how can i sum(without a loop) columns 1:3,4:6,7:9,10:12, to form a new 3x4 matrix?
Is there a general formula that will work for both situations?

Accepted Answer

Stephen23
Stephen23 on 10 Feb 2019
Edited: Stephen23 on 10 Feb 2019
>> M = [1,5,2,4,3,2;2,3,1,4,4,1;4,5,2,2,3,1]
M =
1 5 2 4 3 2
2 3 1 4 4 1
4 5 2 2 3 1
>> M(:,1:2:end) + M(:,2:2:end)
ans =
6 6 5
5 5 5
9 4 4
>> reshape(sum(reshape(M.',2,[]),1),[],3).'
ans =
6 6 5
5 5 5
9 4 4
And
>> M = [2,1,2,1,1,5,5,4,4,2,4,5;3,5,1,3,1,2,5,3,3,4,5,4;2,4,2,1,5,5,4,3,2,2,1,5]
M =
2 1 2 1 1 5 5 4 4 2 4 5
3 5 1 3 1 2 5 3 3 4 5 4
2 4 2 1 5 5 4 3 2 2 1 5
>> reshape(sum(reshape(M.',3,[]),1),[],3).'
ans =
5 7 13 11
9 6 11 13
8 11 9 8

More Answers (0)

Categories

Find more on Loops and Conditional Statements in Help Center and File Exchange

Community Treasure Hunt

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

Start Hunting!