Sum every n-th row in table

Question

chiefjia 2021-10-18

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1566131-sum-every-n-th-row-in-table

编辑： chiefjia 2021-10-21

Dear MATLAB experts,

I'm trying to sum 3 rows at a time of a table column and create a new varible in another table with the values of the sums of the other table. I have found the following post that deals with this: https://de.mathworks.com/matlabcentral/answers/409290-how-can-i-sum-every-nth-row. However, this code only works with arrays and I'm trying to do apply this approach to a table, which I haven't managed to do.

I'm trying to sum 3 rows at a time from the column nr. 8 of the table 'abnormalReturnsTable90' and displaying each one of these sums in a row at a time of column nr. 3 in 'carTable'.

Thank you in advance

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Answer 1

Sahil Jain 2021-10-21

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https://ww2.mathworks.cn/matlabcentral/answers/1566131-sum-every-n-th-row-in-table#answer_813278

Hi. You can use the same approaches that have been suggested in the answers that you have linked. The only difference would be that to access data in a table, curly braces "{}" would be used instead of parenthesis "()". For example,

A = table(rand(666681,1)); % dummy data
[n,col] = size(A);
index = 1:n;
elem = [repmat(3,1,floor(n/3))];
endv = n-sum(elem);
if(~endv)
    endv = [];
end
index = mat2cell(index,1,[elem,endv])';
B = cell2mat(cellfun(@(x) sum(A{x,:},1),index,'un',0)); % braces used for accessing table data
carTable.newColumn = B;