How to save output(.mat) file for all generated values instead of last values ?

I am trying to run the optimization using the following code. The code runs fine and evey thing is working.

But I wanted to saved all the values of x obtained in all iterations, but only the last value is saved in .mat file (screenshot attached).

I tried using the save after the function ends, but that results in error. Please help me...

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function y = opt(x)

Kp = x(1);

Ki = x(2);

disp(x);

save('pqfile.mat','x')

options = simset ('SrcWorkspace','current','DstWorkspace','current');

out = sim('try_fit',[],options);

y=j;

end

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Thanks & Regards

Sanjeev Gupta

[Mathieu NOE]

hello

the question is a bit unclear - so you have a main code that iterates and calls the function shown above ?

what should be the size of x ? only 2x 1 ? what do you expect to save ?

[Sanjeev Gupta]

Hello Mathieu,

Actually, try_fit is the simulink file containing system.

and the function opt is called in Optimization Toolbox (Genetic Algorithm Solver) to optimize gains Kp and Ki of the system.

And variable x has 2 values per iteration (Kp and Ki)..

And I want to save all pairs of Kp and Ki (x(1) and x(2)) generated during optimization.

[Mathieu NOE]

hello again

so to me x is the ouput of another function ? (from the Optimization Toolbox )

in that case you can have a code that concatenates the previous x pair with a new one like :

% init 
X = [];

% maybe here for or while loop 
% your Optimization Toolbox funtion here 
x = stuff(...); % 
y = opt(x); % where is y used - in the above function ? 
X = [X; x(:)]; % concatenation of previous and current x values 
% end of for / while loop
    

does it make sense to you ?

Answer 1

[Walter Roberson]

function y = opt(x)
Kp = x(1);
Ki = x(2);
disp(x);

filename = 'pqfile.mat';
if ~exist(filename)
    pqsave.x = [];
else
    pq = load(filename, 'x');
    pqsave.x = pq.x;
end
pqsave.x(end+1) = x;
save(filename, '-struct', pqsave);

options = simset ('SrcWorkspace','current','DstWorkspace','current');
out = sim('try_fit',[],options);
y=j;
end

This is not efficient. More efficient would be

function y = opt(x)
persistent pqsave
if isempty(pqsave); pqsave.x = []; end

Kp = x(1);
Ki = x(2);
disp(x);

filename = 'pqfile.mat';
pqsave.x(end+1) = x;
save(filename, '-struct', pqsave);

options = simset ('SrcWorkspace','current','DstWorkspace','current');
out = sim('try_fit',[],options);
y=j;
end

but even more efficient would be

function [y, saved_x] = opt(x)
persistent pqsave
if isempty(pqsave); pqsave.x = []; end

if nargout > 1
    y = [];
    saved_x = pqsave.x;
    return
end

Kp = x(1);
Ki = x(2);
disp(x);

pqsave.x(end+1) = x;

options = simset ('SrcWorkspace','current','DstWorkspace','current');
out = sim('try_fit',[],options);
y=j;
end

To use this, call opt as usual with a single output. Then after that is all finished, call it once with two outputs (no inputs needed). Ignore the first output, and the record of the x values will be in the second output. This avoids doing all the save() operations.