How to count the number of pixels having values in 3Dtime series data?

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Vedanta 2024-3-15

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https://ww2.mathworks.cn/matlabcentral/answers/2094836-how-to-count-the-number-of-pixels-having-values-in-3dtime-series-data

评论： Vedanta 2024-3-17

Hello everyone,

I have 3D time series data (180 x 360 x 120), where 180 is latitude, 360 is longitude and 120 is number of months.

For every month, I want to count how many pixels are having values because in every month data is not available for all the 180x360 pixels.

For example: In january there are 100 pixles having data, feb = 115, march = 1224, april = 447, may = 995

Accordingy my 2D output will be : Out = [100 115 1224 447 995];

Thanks

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Answer 1

Pratyush Swain 2024-3-15

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https://ww2.mathworks.cn/matlabcentral/answers/2094836-how-to-count-the-number-of-pixels-having-values-in-3dtime-series-data#answer_1426001

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Hello Vedanta,

Given that you have a 3D time series data and you want to create a 2D output containing count of valid pixel values each month, you can refer to following example implementation:

% Assuming data of 3D timeseries is of dimension: 180 x 360 x 12 --> 12 is referring to the number of months here 
% Example timeseries object with random data %
ts = timeseries(rand(180, 360, 12))
  timeseries

  Common Properties:
            Name: 'unnamed'
            Time: [12x1 double]
        TimeInfo: tsdata.timemetadata
            Data: [180x360x12 double]
        DataInfo: tsdata.datametadata
% Accessing Data property %
data=ts.Data;
% Introducing some NaNs as an example of missing data %
data(data < 0.5) = NaN; 
% Preallocate the output array for performance
Out = zeros(1, size(data, 3))
Out = 1x12
     0     0     0     0     0     0     0     0     0     0     0     0
% Loop through each month and count non-NaN pixels
for month = 1:size(data, 3)
    % Count the number of non-NaN elements for the current month
    Out(month) = sum(~isnan(data(:, :, month)), 'all');
end
% Display the result
disp(Out);
       32512       32488       32525       32545       32406       32425       32428       32251       32317       32313       32290       32531