Help with Nested Structures Preallocation of data or how to clear Nested Structures inside of every loop.

I need to prelocate data in this type of Nested Structures. I didn't find any easy way exept for doing it in backwards for loops. Is there a better way?

ControlResults_con(ControlCycleNumber_con).Quality = rms(y_con(k-LengthOfControlCycle+1:k));
ControlResults_con(ControlCycleNumber_con).Parameters.P = P_control_con;
ControlResults_con(ControlCycleNumber_con).Parameters.D = D_control_con;
ControlResults_con(ControlCycleNumber_con).Parameters.I = I_control_con;

Answer 1

[Satwik]

Hello,

You can efficiently preallocate your nested structure without relying on backward loops by using the following method:

1. Define a template structure with default values.
2. Use the ‘repmat’ function to replicate this template, forming an array of structures.

Here is an example of how you can implement this:

% Define the number of control cycles
numControlCycles = 100; % Example number

% Define a template structure with default values
template.Quality = NaN; % or 0, or any default value you prefer
template.Parameters.P = NaN;
template.Parameters.D = NaN;
template.Parameters.I = NaN;

% Preallocate the structure array
ControlResults_con = repmat(template, numControlCycles, 1);

% Now you can fill in the values in a loop
for ControlCycleNumber_con = 1:numControlCycles
    % Example calculations or assignments
    ControlResults_con(ControlCycleNumber_con).Quality = rms(y_con(k-LengthOfControlCycle+1:k));
    ControlResults_con(ControlCycleNumber_con).Parameters.P = P_control_con;
    ControlResults_con(ControlCycleNumber_con).Parameters.D = D_control_con;
    ControlResults_con(ControlCycleNumber_con).Parameters.I = I_control_con;
end

For more information on the ‘repmat’ function you can refer to this documentation:

https://www.mathworks.com/help/releases/R2022b/matlab/ref/repmat.html.

This method is more efficient than dynamically expanding the structure array within a loop, as it prevents repeated memory allocation.