Sum up measurements to daily basis (measurements each 10 minutes)

Hi,

I want to sum up measurements (of precipitation), that is measured each 10 minutes in one month, to a daily basis.

Sometimes there is a whole in the dataset, but each measurement is related to a date in the format 'yyyy-mm-ddTHH:MM:SSZ'.

I have already converted the date format to a number with the help of the function datenum.

The time and measurements is in a table of the size 4464x2, which corresponds to measurements each 10 minutes in one month (other datasets is of the size 2518x2).

Column 1 is the time and column 2 is the amount of precipitation.

How do I easily sum up, so that I get the amount of precipitation in one day over a month (corresponding to 30 to 31 rows)?

Answer 1

[ag]

Hi Emma,

To sum up the precipitation measurements on a daily basis from a dataset where each measurement is taken every 10 minutes, you can use MATLAB's "dateshift" function to extract the date from the datetime and then use MATLAB's "groupsummary" function to sum the precipitation for each day.

The below code snippet explains how to achieve this using dummy data:

%dummy data
numMeasurements = 4464;
startDate = datenum(2023, 1, 1, 0, 0, 0);
datenumArray = startDate + (0:10:(numMeasurements-1)*10)'/1440;
precipitationArray = rand(numMeasurements, 1); % Random precipitation values
T = table(datenumArray, precipitationArray, 'VariableNames', {'Datenum', 'Precipitation'});

% Convert 'Datenum' to 'datetime'
T.Time = datetime(T.Datenum, 'ConvertFrom', 'datenum');

% Add a new column to group by date
T.Date = dateshift(T.Time, 'start', 'day');

% Sum the precipitation for each day
dailyPrecipitation = groupsummary(T, 'Date', 'sum', 'Precipitation');

% Display the result
disp(dailyPrecipitation);

       Date        GroupCount    sum_Precipitation
    ___________    __________    _________________

    01-Jan-2023       144             78.865      
    02-Jan-2023       144              69.27      
    03-Jan-2023       144             70.836      
    04-Jan-2023       144             74.875      
    05-Jan-2023       144             70.657      
    06-Jan-2023       144             72.983      
    07-Jan-2023       144              73.88      
    08-Jan-2023       144             71.338      
    09-Jan-2023       144             70.672      
    10-Jan-2023       144             70.006      
    11-Jan-2023       144             80.142      
    12-Jan-2023       144             69.565      
    13-Jan-2023       144             65.849      
    14-Jan-2023       144             76.129      
    15-Jan-2023       144             76.818      
    16-Jan-2023       144             73.713      
    17-Jan-2023       144             71.427      
    18-Jan-2023       144             77.961      
    19-Jan-2023       144             78.999      
    20-Jan-2023       144             67.977      
    21-Jan-2023       144             68.104      
    22-Jan-2023       144             78.649      
    23-Jan-2023       144             68.548      
    24-Jan-2023       144             72.169      
    25-Jan-2023       144             71.941      
    26-Jan-2023       144             76.214      
    27-Jan-2023       144             70.235      
    28-Jan-2023       144             73.883      
    29-Jan-2023       144             72.191      
    30-Jan-2023       144              69.82      
    31-Jan-2023       144             74.523      

For more details, please refer to the following MathWorks documentations:

• datetime - https://www.mathworks.com/help/matlab/ref/datetime.html
• dateshift - https://www.mathworks.com/help/matlab/ref/datetime.dateshift.html
• groupsummary - https://www.mathworks.com/help/matlab/ref/double.groupsummary.html

Hope this helps!