MATLAB: How to convert 3d monthly data into season

3dconvertMATLAB

Example of my data set is 56*42*360 (30 years) and each page represent a month for example 56*42*1 mean jan 1980 and 56*42*13 means jan 1981. I want to get only seasonal value not the number of months in a season, we have to define season as spring(mar, apr ,may), summer(jun,jul,aug) and so on.

I found a relevant solution here but it gives only number of months of a single season. I need seasons in staright as spring of 1980…….to autumn of 2010.

Expected outcome is something like 56*42*119.

Best Answer

How about the following?

% Sample data
Data = rand(56,42,360);
% Reshape the data so that each row shows monthly data (42*56)
Data = permute(Data,[3 2 1]);
Data = reshape(Data,360,42*56);
% Calculate sum for evely 3 months
group = repelem((1:120)',3);
Data2 = splitapply(@sum,Data, group);
% Reshape the data to the original format
Data2 = reshape(Data2,120,42,56);
Data2 = permute(Data2,[3 2 1]);

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MATLAB: Please help me to correct the for-loop

Behzad - I don't really understand why in your code you have variables named table and then tbl. Perhaps both are the same variable and so there has been a typo in your code. I do recommend against using variable names that are identical to built-in MATLAB function (see table). If you want to loop over each set of 30 year data in your cell array then you could try something like

load ExampleCell.mat;
meanTableDataArray = cell(length(CELL),4);
for j = 1:length(CELL)
    sampleTableData = CELL{j};
    sampleTableData.month = month(sampleTableData.dates);
    sampleTableData.seasons = floor(sampleTableData.month ./3);
    sampleTableData.seasons(sampleTableData.seasons ==4 ) = 0;
    sampleTableData.seasons = categorical(sampleTableData.seasons, [0 1 2 3], ["Spring", "Summer", "Autumn", "Winter"]);
    [group, mean_table] = findgroups(sampleTableData(:, 'seasons'));
    mean_table.rrr24 = splitapply(@sum, sampleTableData.rrr24, group);
    for k = 1:4
        meanTableDataArray{j,k} = mean_table(k,:); % extracts as a table
    end
end

I haven't tested the above but I think that it will give you an idea of what you can do. Note how it is more similar to the first block of code that you posted, and that the only indexing we use (with j) is when we extract the jth table data.

MATLAB: Daily 3d array to monthly- dealing with alternate days in a month and leap years – How to do it

You don't have another option than just hardcoding the number of days in a month. You can do this in a fancy way using the date functions in Matlab, or just look at a calender. The fact that you have 365 days means that you are dealing with a non-leap year, so February only has 28 days.

There are probably simpler ways to solve it, but you can easily convert this 3D matrix to a cell array, apply the function you already suggested to each cell and then convert back to a 3D matrix.

A=rand(720,360,365);%generate example array
month_lengths=[31 28 31 30 31 30 31 31 30 31 30 31];%non-leap year
B=mat2cell(A,size(A,1),size(A,2),month_lengths);%divide into 1 cell per month
B=cellfun(@(x) mean(x,3),B,'UniformOutput',false);%find mean for each month
B=cell2mat(B);%convert back to 3D array

Best Answer

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