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Start Cumsum from table of values that correspond with given indeces

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Hello, I have a timetable of values called ddtable with column 'RAIN' and an array of index called startdd.
The objective:
1) If index of ddtable matches with startdd, start cumsum for subsequent RAIN values until it exceeds 3.5 then stop.
2) Append all indices that were involved in the cumsum into a new table
How do I go about this because traditional while loop does not work as well and no discussion have addressed this type of question.
for ii = 1:length(rain)
% If rain index matches with startdd, start cumulation
if idx(rain) == startdd
% The cumulation will end once it exceeds 3.5mm
while cumsum(rain(startdd)) < 3.5
% Append all index values that were involved in the cumsum
end
end
end
Many thanks!
  2 Comments
Eric Sofen
Eric Sofen on 18 Dec 2020
The data in your MAT files doesn't match up with your example code, so I'm not 100% sure what you're trying to do, but see if this does the trick.
load('ddtable.mat')
load('startdd.mat')
result =ddtable([],:);
inds = [];
for ii = startdd % Iterate over start indices
cs = cumsum(ddtable.RAIN(ii:end)); %do cumsum over most of the rain data - we'll end up throwing away anything beyond 3.5 mm
inds3_5 = ii-1 + find(cs <= 3.5); % Find where data is below the 3.5mm threshold; adjust based on the start index.
result = [result; ddtable(inds3_5,:)]; % append data
inds = [inds; inds3_5]; % append indices
end
Jonathan Cheong
Jonathan Cheong on 28 Dec 2020
Wow! Thank you very much Eric this is exactly what I was looking for.
However, after studying the results another condition that I thought I had eliminated beforehand emerged.
Condition: The cumsum cannot be less than 4 days.
So for example, there are 3 cumsum instances:
A) 15
B) 60, 61, 62, 63...
C) 70, 72
How do I remove A and C but not B from the result?
Ps: If I have to start a new question let me know.

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