How to save a struct data inside a table ?

Hi everyone,

I wrote a program which consists of two for loop (as shown in figure below). The inner for loop will generate a two - structure data (size - 1x7 ) and one - array data( size - 7x1024) for every iteration of the outer for loop.

I tried to save the inner for loop data using struct method. But I am not able to read the data properly.

So, could you please suggest me a way to save both the struct data and array data together to create a table while iterating the outer for loop

or if could suggest me a better and easier approach to save the data.

Thank you.

% Out for loop 
for k = 1: 4
    % Inner for loop 
    for i = 1: 7

    end
    % 
end

[dpb]

You forgot to show us the actual data structures, themselves...

Answer 1

[Arjun]

Hi @S,

As per my understanding, you want to store struct data and array data being generated by inner for loop into an efficient data structure.

To store and organize struct and table data generated by the inner nested loop, you can use an array of structs where each element of this array is a struct that contains two fields: “structData” and “arrayData”.

Kindly refer to the code below for better understanding of the implementation:

% Create an array of struct for storing the results 

results(4) = struct('structData', [], 'arrayData', []); 

for k = 1:4 

    % preallocate space for saving the data 

    tempStructData = struct('field1', [], 'field2', []);  

    tempArrayData = zeros(7, 1024);  

    for i = 1:7 

        % populate the struct data 

        tempStructData(i).field1 = rand();  

        tempStructData(i).field2 = rand();  

        % Populate the array data 

        tempArrayData(i, :) = rand(1, 1024);  

    end 

    % Store the generated data in the results struct array 

    results(k).structData = tempStructData; 

    results(k).arrayData = tempArrayData; 

end 

% Accessing the data 

for k = 1:4 

    disp(['Data for iteration ', num2str(k)]); 

    disp(results(k).structData); 

    disp(results(k).arrayData); 

end 

This will create the desired structure to efficiently store the data. To convert it into a table will require additional step of converting “structData” and “arrayData” to cell arrays and then creating a table.

Kindly refer to the code snippet below for storing data in a table:

structDataCell = cell(length(results), 1); 

arrayDataCell = cell(length(results), 1); 

 

% Populate cell arrays from the struct array 

for k = 1:length(results) 

    % Store each struct and array in a cell 

    structDataCell{k} = results(k).structData;  % Store the struct array 

    arrayDataCell{k} = results(k).arrayData;    % Store the array data 

end 

resultsTable = table(structDataCell, arrayDataCell, 'VariableNames', {'StructData', 'ArrayData'}); 

disp(resultsTable); 

Kindly read about “cell” arrays and “struct” for more information:

• cell array: https://www.mathworks.com/help/releases/R2021b/matlab/ref/cell.html
• struct: https://www.mathworks.com/help/releases/R2021b/matlab/ref/struct.html

I hope this will help!