Cumulative sum with multiple constraints

Question

Dixi 2019-6-25

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/468772-cumulative-sum-with-multiple-constraints

回答： Dixi 2019-6-25

Hello,

i'm trying to calculate a cumulative sum (of column value) in a table with two constraints in different columns (date, time).

The cumulative sum should add all values for equal dates and timesteps. The amount of values per date and timestep might be variable.

date = [20190101; 20190101; 20190101; 20190101; 20190101; 20190101; 20190101; 20190102; 20190102; 20190102; 20190102; 20190102];
time = [0; 0; 0; 0; 12; 12; 12; 0; 0; 12; 12; 12];
value = [2; 7; 5; 3; 5; 4; 1; 6; 8; 2; 5; 8];
T = table (date, time, value);

The cumulative sum in the fourth column of the table should be like:

csum = [2; 9; 14; 17; 5; 9; 10; 6; 14; 2; 7; 15]

Thanks!

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Answer 1

Kaustav Bhattacharya 2019-6-25

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https://ww2.mathworks.cn/matlabcentral/answers/468772-cumulative-sum-with-multiple-constraints#answer_380686

在 MATLAB Online 中打开

start = 0;
cumulativesum = zeros(height(T),1);
for row = 1:height(T)
    if row == 1
        cumulativesum(row) = T.value(row);
        start = 1;
    elseif T.date(row-1) == T.date(row) && T.time(row-1) == T.time(row)
        cumulativesum(row) = sum(T.value(start:row));
    else
        start = row;
        cumulativesum(row) = T.value(row);
    end
end

'cumulativesum' gives you the result you were looking for.

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Answer 2

Prasanth Sikakollu 2019-6-25

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/468772-cumulative-sum-with-multiple-constraints#answer_380685

在 MATLAB Online 中打开

You can try the following code to get the cumulative sum as fourth column in table T.

date = [20190101; 20190101; 20190101; 20190101; 20190101; 20190101; 20190101; 20190102; 20190102; 20190102; 20190102; 20190102];
time = [0; 0; 0; 0; 12; 12; 12; 0; 0; 12; 12; 12];
value = [2; 7; 5; 3; 5; 4; 1; 6; 8; 2; 5; 8];
csum = [value(1)]   % Initialising the array with value(1)
cur_time = time(1)  % Initialising the current time with time(1)
for i = 2:length(value) 
    if cur_time == time(i)  
        csum = [csum ; csum(i-1) + value(i)]  % finds csum if time(i) is same as cur_time and appends it at the end of csum
    else
        cur_time = time(i)
        csum = [csum ; value(i)]    % updates the cur_time and appends value(i) at the end of csum
    end
end
T = table (date, time, value, csum);