Matlab - Cómo hacer una sumatoria dentro de otra

function [VA]=varianza(A)

S=0;

for i=1:length(A)

    S=S+A(i);

end

VA = (1/length(A))* ?????((A(i)-((1/length(A))*S))^2);

end

function VA=varianza(A)

S=0;

 n=length(A);

for i=1:n

    S1=0;

    for j=1:n

        S1=S1+A(j);

    end

S =S+(A(i)-1/n*S1)^2;

end

VA=1/n*S;

>> A=rand(1,10), VA=varianza(A)

A =

    0.4387    0.3816    0.7655    0.7952    0.1869    0.4898    0.4456    0.6463    0.7094    0.7547

VA =

    0.0369