Sum of all the elements after the matrix diagonal

Question

Dmitriy 2020-3-9

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/509858-sum-of-all-the-elements-after-the-matrix-diagonal

编辑： Dmitriy 2020-3-9

Hello. I am trying to calculate the total sum of all the elements in any given matrix, including row array and column array, starting from the cell where the row index is equal to column index (matrix diagonal). I am picking up an extra value in my code, and I don't know why. Here is my code:

(function syntax with a matrix given)

(getting the number of the elements in the matrix using the "size" function)

(initializing my output count "answer")

for r = 1:row
    for c = 1:col
        if col >= row
            answer = col + answer;
        end
    end
end

So for a matrix A [1 2 3; 4 5 6; 7 8 9], the answer should be 26 and I am getting 27 and I can't figure why. I've tried to use the "sum" function but it gets just way to complicated and I get lost with referencing of the columns/rows. Also I must use the "for loop" and no super fancy build-in functions.

2 个评论
显示无隐藏无

Matt J 2020-3-9

编辑：Matt J 2020-3-9

在 MATLAB Online 中打开

Also I must use the "for loop" and no super fancy build-in functions.

It is absurd to call this "super fancy",

>> sum(  triu(A), 'all')
ans =
    26

Dmitriy 2020-3-9

Thanks Matt, but:

"Assessment result: incorrect [1 2 3; 4 5 6; 7 8 9]

The submission must not contain the following functions or keywords: triu"

That's why said "no super fancy build-in functions". I wish I could use them but the solution must be based on "for... loop" function only.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Matt J 2020-3-9

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/509858-sum-of-all-the-elements-after-the-matrix-diagonal#answer_419241

编辑：Matt J 2020-3-9

在 MATLAB Online 中打开

answer=0;
for r = 1:row
    for c = 1:col
        if c >= r
            answer = A(r,c) + answer;
        end
    end
end

answer =
    26

5 个评论
显示 3更早的评论隐藏 3更早的评论

Matt J 2020-3-9

Yes, an unfortunately misleading test case.

Dmitriy 2020-3-9

编辑：Dmitriy 2020-3-9

That's the code I wrote in the first 15 minutes of thinking about the problem, but I was getting the wrong answers with it, so I abondoned the idea completly.

P.S. I ran your code and found out that I had previously the iverted logic and that's why mine didn't work. Thanks, man! Problem solved.

请先登录，再进行评论。