Daywise differences in array

Hi @Poulomi,

To address your request for analyzing the rainfall data and determining whether the difference in rainfall values exceeds 30 mm within a 24-hour period, we need to modify the approach slightly. Your initial code iterates through each time point but only checks the next day's value, rather than considering all values within the previous 24 hours. This requires a more efficient method that avoids nested loops. You can utilize MATLAB’s capabilities with timetables to streamline this process. The following code implements a more efficient approach using logical indexing and vectorized operations:

% Input data as provided
R = [1982	5	1	3	25;
   1982	5	1	6	30;
   1982	5	1	12	35;
   1982	5	1	18	40;
   1982	5	2	0	45;
   1982	5	2	3	45;
   1982	5	2	6	50;
   1982	5	2	12	55;
   1982	5	2	18	55;
   1982	5	3	0	60;
   1982	5	3	3	65;
   1982	5	3	6	80;
   1982	5	3	12	90;
   1982	5	3	18	105;
   1982	5	4	0	115;
   1982	5	4	3	115;
   1982	5	4	6	115;
   1982	5	4	12	115;
   1982	5	4	18	115;
   1982	5	5    3   30];

% Create a timetable
ttR = timetable(datetime(R(:,1:3)) + hours(R(:,4)), R(:,5),
'VariableNames', 
{'Rainfall'});

% Initialize variables to hold results
t = [];
r = [];

% Loop through each time point
for i = 1:height(ttR)
  % Define the time window for the previous 24 hours
  startTime = ttR.Time(i) - caldays(1);
  endTime = ttR.Time(i);

    % Find all rainfall values within this time window
    rainInWindow = ttR.Rainfall(ttR.Time >= startTime & ttR.Time <
    endTime);

    if ~isempty(rainInWindow)
        % Calculate the difference between current rainfall and 
        maximum in window
        dRF = max(rainInWindow) - ttR.Rainfall(i);

        if dRF > 30
            t = [t; ttR.Time(i)];
            r = [r; dRF];
        end
    end
  end

% Create result timetable
ttDRF = timetable(t, r, 'VariableNames', {'24hr_Rainfall'});
ttDRF.Properties.DimensionNames(1) = {'Begin_Date'};

% Display results
disp(ttDRF);

first timetable is created from your data which allows for easier time-based indexing. For each time point, we calculate the start and end of the previous 24-hour window, using logical indexing to extract all rainfall values within that time window, computing the difference between the maximum rainfall in that window and the current time's rainfall. If the difference exceeds 30 mm, we store the timestamp and difference.

Feel free to run this code snippet in your MATLAB environment, and it should yield results based on your specified criteria for identifying significant rainfall differences over a defined time frame.