Expand Struct Array Elements Rowwise

Hi everyone,

is there a possibility in Matlab to epand a existing structy array rowwise ?

Example for one Field Element

for i=1:Steps:End
    [Output.temp.Results]=fun(Input);
    Output.Curve.Results.A(i,:)=Output.temp.Results.A
end

Now my Struct Array has about 50 Fieldelements. Is there an elegant way to do this in a few lines?

Thans for your help.

Answer 1

[Yukthi S]

Hi Jens Olschewski

I got that you wanted to expand the Struct array from one field element to 50 field elements. For that, you need to use a For loop in the function “fun” definition.

Since you did not provide any information about the rest of the code ,I am assuming some input values and also “fun” definition.

You can refer the following code which is verified in MATALB R2019a, to get a struct array with 50 field elements:

% Define Steps and End
Steps = 1;
End = 5;

% Initialize an empty struct for Output.Curve.Results
Output.Curve.Results = struct();

for i = 1:Steps:End
    % Call the function and get the temporary results
    Output.temp.Results = fun(i);  % 'i' is passed as an input for the example
    
    % Dynamically expand each field
    fieldNames = fieldnames(Output.temp.Results);
    for j = 1:numel(fieldNames)
        fieldName = fieldNames{j};
        
        % Check if the field already exists in Output.Curve.Results
        if isfield(Output.Curve.Results, fieldName)
            % Expand the field row-wise
            Output.Curve.Results.(fieldName)(end+1,:) = Output.temp.Results.(fieldName);
        else
            % Initialize the field in Output.Curve.Results
            Output.Curve.Results.(fieldName)(1,:) = Output.temp.Results.(fieldName);
        end
    end
end

% Display the structure of the final struct array
disp(fieldnames(Output.Curve.Results));

    {'Field1' }
    {'Field2' }
    {'Field3' }
    {'Field4' }
    {'Field5' }
    {'Field6' }
    {'Field7' }
    {'Field8' }
    {'Field9' }
    {'Field10'}
    {'Field11'}
    {'Field12'}
    {'Field13'}
    {'Field14'}
    {'Field15'}
    {'Field16'}
    {'Field17'}
    {'Field18'}
    {'Field19'}
    {'Field20'}
    {'Field21'}
    {'Field22'}
    {'Field23'}
    {'Field24'}
    {'Field25'}
    {'Field26'}
    {'Field27'}
    {'Field28'}
    {'Field29'}
    {'Field30'}
    {'Field31'}
    {'Field32'}
    {'Field33'}
    {'Field34'}
    {'Field35'}
    {'Field36'}
    {'Field37'}
    {'Field38'}
    {'Field39'}
    {'Field40'}
    {'Field41'}
    {'Field42'}
    {'Field43'}
    {'Field44'}
    {'Field45'}
    {'Field46'}
    {'Field47'}
    {'Field48'}
    {'Field49'}
    {'Field50'}

function result = fun(input)
    % Initialize an empty struct
    result = struct();
    
    % Loop through to create 50 fields with random numbers
    for k = 1:50
        fieldName = sprintf("Field%d", k);  % Generate field name dynamically
        result.(fieldName) = rand(1, 1);    % Assign a random number to the field
    end
end

You can refer to the following MATLAB documentation to have more information on "fieldnames":https://in.mathworks.com/help/releases/R2019a/matlab/ref/fieldnames.html?searchHighlight=fieldnames&s_tid=doc_srchtitle