Dynamic arrays error message

Question

Abner Ojeda 2020-5-17

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/526018-dynamic-arrays-error-message

评论： Abner Ojeda 2020-5-19

Hey everyone,

I have many variables in my code that increase their size with a for bucle, and I've been realized of the code assistance adverticement. I read the advice and try to apply it, but I couldn't solve it. I am trying to solve ir because it's going to be and extens code and I'm try to not expend many resources in that kind of things. (I know that my code isn't optimum, jaja) but that's really bugging me.

Thanks for your help and have a great day.

P.S: This is the suggestion "Variable 'name of the variable' appers to change size on every loop iteration"

Dhx=[];
Dgx=[];
Dfx=[];
for s=x(1:end)
    gh= diff(hx, (s));
    gg= diff(gx, (s));
    gf= diff(func, (s));
    Dfx=[Dfx, gf];
    Dhx=[Dhx, gh];
    Dgx=[Dgx, gg];
end

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Answer 1

Ameer Hamza 2020-5-17

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/526018-dynamic-arrays-error-message#answer_432875

编辑：Ameer Hamza 2020-5-17

在 MATLAB Online 中打开

Try changing to something like this

Dhx=cell(1,numel(x));
Dgx=cell(1,numel(x));
Dfx=cell(1,numel(x));
for i=1:numel(x)
    Dhx{i} = diff(hx, x(i));
    Dgx{i} = diff(gx, x(i));
    Dfx{i} = diff(func, x(i));
end
Dhx = [Dhx{:}];
Dgx = [Dhx{:}];
Dfx = [Dhx{:}];

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Abner Ojeda 2020-5-17

在 MATLAB Online 中打开

Sure, I left you my code below. Ok, Walter, thanks for the answer, maybe I had a mistake copying Ameer's code, I'm going to try again.

Thanks for take your time in answer my question.

P.S: As you can see, I have many variables of this type and that's the most important reason I'm trying to optimize it (at least that part xD)

%%Creación de variables.
clear; close all; clc;
Dhx=[]; Dgx=[]; Dfx=[];
rh=[]; rg=[];
Dhhx=[]; Dggx=[];
KKT=[];
%%Solicitud de función
var= input ('Ingrese el num de var:\n');
syms x [1 var];
func= input ('Ingrese la función la función objetivo: \n');
%%Solicitud de restricciones de igualdad
resi= input ('Ingrese el numero de restricciones \nde igualdad: ');
syms l [1 resi];
for t=1:resi
    resth= input(['Ingrese la restricción \nde igualdad ', num2str(t)]);
    hx=[rh,resth];
end
%%Solicitud de restricciones de desigualdad
resd=input ('Ingrese el numero de restricciones \nde desigualdad: ');
syms m [1 resd];
for u=1:resd
    restg=input(['Ingrese la restricción \nde desigualdad ', num2str(u)]);
    gx=[rg, restg];
end
%%Calcúla las derivadas parciales respecto x1, x2...xn y se almacenan.
for s=x(1:end)
    gh= diff(hx, (s));
    gg= diff(gx, (s));
    gf= diff(func, (s));
    Dfx=[Dfx, gf];
    Dhx=[Dhx, gh];
    Dgx=[Dgx, gg];
end
%KKT: Dfx+l·Dhx+m·Dgx=0
for q=1:numel(Dhx)
    ff= l.*Dhx(1,q);
    Dhhx=[Dhhx, ff];
end
for q=1:numel(Dhx)
    ff= m.*Dgx(1,q);
    Dhhx=[Dhhx, ff];
end
for p=1:numel(Dfx)
    KKT1= (Dfx(1,p)+Dhhx(1,p)+m*Dgx(1,p));
    KKT=[KKT, KKT1];
end