Unable to perform assignment because the left and right sides have a different number of elements.

Hello

I try to collect results of function in a vector, but there is error "Unable to perform assignment because the left and right sides have a different number of elements".

I tried also use "reshape (f,[],1), but it doesn't help.

Mr=2;
Mt=2;
Rt=eye(Mr);
Rr=[1 08;0.8 1];
K=0;
Hw=(randn(Mr,Mt)+1i*randn(Mr,Mt))./sqrt(2);
H=sqrt(1/(K+1))*sqrtm(Rr)*Hw*sqrtm(Rt');
N=1000;
gamma=zeros(Mt,1)

gamma = 2×1

0 0

for SNR=0:1:15
    
    for k=1:1:N
        Hw=(randn(Mr,Mt)+1i*randn(Mr,Mt))./sqrt(2);
        X = Hw*Hw';
        r=rank(X);
        e = eig(X)
        for i=1:r
            p=1;
            gamma(i)=(f(r,p,Mt,SNR,e));
            Cclosed=sum(log2(1+SNR*gamma(i)/Mt*e(i)));
        end
        R(k)=Cclosed;
    end
    stem(SNR,mean(R))
    xlabel("SNR  [dB]");
    ylabel("Ergodic Capacity  [bits/s/Hz]");
    hold on;
end

e = 2×1

0.2882 2.6803

Unable to perform assignment because the left and right sides have a different number of elements.

function Wp=f(r,p,Mt,SNR,e)
for i=1:1:r-(p-1)
    wl=1/(r-(p-1))*(Mt+Mt/SNR*sum(1/e(i)));
end
for i=1:1:Mt
    Wp(i)=wl-(Mt/SNR*1/e(i));
    
    
    
    if Wp(i)<=0
        Wp(i)=[];
    end
    
    if sum(Wp)~=Mt
        p=p+1;
    else end
end
end

Answer 1

[Image Analyst]

In

gamma(i)=(f(r,p,Mt,SNR,e));

f returns a variable Wp, which is a vector of MT elements. How are you thinking that you're going to stick it in the single, i'th element of gamma? Also, gamma is a built in function so don't use it as the name of your variable. Call it theGamma or something. Maybe theGamma should be a 2-D matrix with Mt columns

theGamma = zeros(1, Mt) % Call this BEFORE the loops start.

and then you can fill up the whole row

Wp = f(r,p,Mt,SNR,e); % A 1 x Mt row vector.
theGamma(i, :)= Wp; % Stuff Wp into the i'th row of theGamma

Also, see the FAQ for a discussion of the error:

https://matlab.fandom.com/wiki/FAQ#%22In_an_assignment_A(I)_=_B,_the_number_of_elements_in_B_and_I_must_be_the_same%22

[Ruslan Askarov]

Thank you Man! it works

Answer 2

[Parag Jhunjhunwala]

Hi Ruslan Askarov,

This question has already been answered here:

https://www.mathworks.com/matlabcentral/answers/439046-unable-to-perform-assignment-because-the-left-and-right-sides-have-a-different-number-of-elements