Cumulative sum with multiple constraints

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!

Answer 1

[Kaustav Bhattacharya]

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.

Answer 2

[Prasanth Sikakollu]

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);

Hope this helps in solving your problem

Answer 3

[Dixi]

Both answers are working fine.

Thank you!