Summation using symsum of matrix

How can l use MATLAB to do the summation as shown above? i=1, n=5, x and y are variables, Sij is a nxn matrix, beta and gamma are constant. I tried to use symsum but the MATLAB does not allow me to exctract the element in the matrix Sij or in the vector x and y. The code i tried is:

symsum(S(1,j)*(x(j)-beta*u(j))-gamma*(x(1)-betay(1)

Could you help me please.

[Gaurav Aggarwal]

I haven't anywhere seen symsum doing the indexing in a structured data. Do you have to use symsum only?

I believe something on the following lines could be helpful, please do verify if the following equation does what you are trying to do.

sum(S(i,1:n) .* (x(1:n) - beta*y(1:n)) - gamma * (x(i) - beta*(y(i))))