Finding sum of all the elements in a row corresponding to an element which is less than a certain value?

Question

Mohammad Zaved Siddiqui 2016-11-21

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/313276-finding-sum-of-all-the-elements-in-a-row-corresponding-to-an-element-which-is-less-than-a-certain-va

评论： Mohammad Zaved Siddiqui 2016-11-21

采纳的回答： Alexandra Harkai

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I have a matrix which looks like this:

[1 0 3; 9 1 5; 6 0 9; 2 4 6; 5 2 0]

I want to find the sum of all the elements in column 2 and 3 if the corresponding element in column 1 is less than 3. For example: In column 1, 1 and 2 are less than 3 so the result should be the sum of all the rest of the elements of rows corresponding to 1 and 2 and the answer should be (0+3+4+6)=13. How can I do that in Matlab 2016a?

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Answer 1

Alexandra Harkai 2016-11-21

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/313276-finding-sum-of-all-the-elements-in-a-row-corresponding-to-an-element-which-is-less-than-a-certain-va#answer_244119

编辑：Alexandra Harkai 2016-11-21

在 MATLAB Online 中打开

a = [1 0 3; 9 1 5; 6 0 9; 2 4 6; 5 2 0];
sum(sum( a(a(:,1)<3, 2:3) ))

a(:,1)<3 created a binary vector to indicate which rows satisfy the condition, a(a(:,1)<3, 2:3) creates the resulting array of elements to sum, then sum(sum()) adds up the results in both directions.