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

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Sanjeev Gupta
Sanjeev Gupta 2021-3-8
评论： Mathieu NOE 2021-3-10
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...
-----------------------------------------------------------------------------------------------
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
-----------------------------------------------------------------------------------------------
Thanks & Regards
Sanjeev Gupta
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Sanjeev Gupta
Sanjeev Gupta 2021-3-9
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
Mathieu NOE 2021-3-10
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 ?

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回答（1 个）

Walter Roberson
Walter Roberson 2021-3-9
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.

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