I am facing problem regarding storage of values for d() using for loop which is of 100x100 size for each iteration of a and k.

Question

Maimoona Asad 2021-12-19

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1614085-i-am-facing-problem-regarding-storage-of-values-for-d-using-for-loop-which-is-of-100x100-size-for

回答： Jan 2021-12-19

clc
clear all
close all
%% Cell generation
alpha=4;   % pth loss exponent
p=-30;      % power= 10db
p_lin=db2pow(p);
radius=15;
lambda=0.6;
l=lambda/2;
alpha=(lambda/(4*pi))^2;
elements=10;
L=12;
N=4;
K=4;
%%  Large intelligent reflecting surfaces
X3=[-7.655; -6.189; -3.251; 2.926; 6.534; 10.79; 5.203; -4.465; 1.42; -8.66; -0.8748; 6.534] ;
Y3=[1.393; 10.42; 6.639; 5.821; 8.425; 2.924; 1.139; 0.7508; -7.917; -6.928; -10.01; -7.03];
plot(X3,Y3,'r*','MarkerSize', 10, 'Linewidth', 2);
%legend('','Base stations','Users','Intelligent Reflecting Surfaces')
hold on
elements=10;
p=0;
%% loop for the elements of irs% D=zeros(1,1200);
for t=1:L
    for v=1:elements
        for w=1:elements
            x3(v,w) = X3(t,1)+p; % X coordinate of an element of IRS for plotting
            x_e = zeros(10,10, 12);
            y_e = zeros(10,10,12);
            y3(v,w) = Y3(t,1);     % Y coordinate of an element of IRS for plotting
            p=w*l;   
            x_e(v,w,t) =x3(v,w);   
            y_e(v,w,t)= y3(v,w);
        end
        p=0;
        Y3(t,1) = Y3(t,1) + l;
    end
    plot(x3,y3,'bo')
    %      B=x_e(:,:,1)';
    %      C=reshape(B,1,[]);
end
%% loop to evaluate distance between IRS and IRS
for a=1:L-1
    dd=a;
    for k=a+1:L-1
        bb=k+1;
        for l=1:elements
            for m=1:elements
                for n=1:elements
                    for o=1:elements
                        d(a,bb)=sqrt((x_e(n,o,k)-x_e(l,m,a))^2+(y_e(n,o,k)-y_e(l,m,a))^2)
                    end
                end
                
            end
        end
    end
    
end

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Walter Roberson 2021-12-19

在 MATLAB Online 中打开

You should be using a 4 dimensional d array such as

d(a,bb,n,o)=sqrt((x_e(n,o,k)-x_e(l,m,a))^2+(y_e(n,o,k)-y_e(l,m,a))^2);

Except that I would suggest creating a local 2D array in the inner loop, like

for a=1:L-1
    dd=a;
    for k=a+1:L-1
        bb=k+1;
        for l=1:elements
            for m=1:elements
                t = zeros(elements, elements);
                for n=1:elements
                    for o=1:elements
                        t(n,o)=sqrt((x_e(n,o,k)-x_e(l,m,a))^2+(y_e(n,o,k)-y_e(l,m,a))^2);
                    end
                end
                dd(a,bb,:,:) = t;
            end
        end
    end
    
end

That would be more efficient.

Maimoona Asad 2021-12-19

i am getting all values 0 after trying this

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Answer 1

Jan 2021-12-19

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1614085-i-am-facing-problem-regarding-storage-of-values-for-d-using-for-loop-which-is-of-100x100-size-for#answer_858615

在 MATLAB Online 中打开

You overwrite the data by zeros repeatedly:

for t=1:L
    for v=1:elements
        for w=1:elements
            % Here all formerly written values of x_e and y_e
            % are overwritten with zeros. Only the last iteration
            % is kept:
            x_e = zeros(10,10, 12);
            y_e = zeros(10,10,12);
            x_e(v,w,t) =x3(v,w);   
            y_e(v,w,t)= y3(v,w);
        end
    end
end