# Optimization Problem about Optimal Portfolio with Aversion Index

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KA HEI LAM 2019 年 2 月 4 日
Commented: Alan Weiss 2019 年 2 月 4 日
Hello everyone, I'm trying to due with following optimization problem:
I have done some of the coding but cannot finish the double summation part.
Does anyone have any ideas that could help??? Thanks in advance.

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Alan Weiss 2019 年 2 月 4 日
I don't see your rho and sigma variables, but you could try
sumexpr = optimexpr;
for i = 1:n
for j = 1:n
sumexpr = sumexpr + w(i)*w(j)*rho(i,j)*sigma(i)*sigma(j);
end
end
It would undoubtedly be more efficient to write this double summation as a standard MATLAB matrix multiplication, something like
sumexpr = w'*M*w;
where M has an appripriate definition, but the double sum should work, too.
Alan Weiss
MATLAB mathematical toolbox documentation

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KA HEI LAM 2019 年 2 月 4 日
Thanks for the reply. I tried the following double summation:
w'*ann_std'*corrlation*ann_std*w
but there is an error:
Error using optim.internal.problemdef.MatrixOperator
Inner matrix dimensions must agree.
Error in optim.internal.problemdef.Mtimes
Error in *
I have calculated the rho and sigma with n-by-n and 1-by-n matrix respectively. Is there any problem?
Alan Weiss 2019 年 2 月 4 日
I suggest that you use the debugger to find out what sizes the variables have just before the times operation executes.
Alan Weiss
MATLAB mathematical toolbox documentation

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