How to perform calculations using a structure array ?

Hello everyone, I have a structure array named model with 26 fields, with S (metabolites as rows and reactions as columns) as one of the fields. For each column of S, I want to check whether the sum is zero. If it is zero, I want to feed the index of the respective column into another field in the same structure, model.reactions and combine all such reactions to an output named transport.

Could someone help me?

Answer 1

[BhaTTa]

Hey @Priyadharshini Kannan, I assume that 'model' is your structure with a field 'S' which is a matrix and another field 'reactions' which is a cell array. Below I have provided the code where I have initialized the value of S with dummy values

% Define a structure named 'model'
model = struct();

% Create a modified S matrix with a column that sums to zero
model.S = [
    -2,  2,  3,  5, -1; 
     0,  4,  5,  0, -1;
     0,  0,  0, -4, -1;
     5, -5, -2, -2,  1;
    -3, -1, -6,  1,  2   
];


disp('Modified S matrix:');
disp(model.S);


zeroSumIndices = [];


numColumns = size(model.S, 2);


for col = 1:numColumns
    % Check if the sum of the column is zero
    if sum(model.S(:, col)) == 0
        % If the sum is zero, append the index to zeroSumIndices
        zeroSumIndices(end + 1) = col;
    end
end

% Store the indices of zero-sum columns in the model.reactions field
model.reactions = zeroSumIndices;

% Combine all such reactions into an output named 'transport'
transport = model.reactions;

% Display the transport array
disp('Indices of columns with zero sum (transport):');
disp(transport);

Hope it helps.