Evaluate elementary symmetric polynomials

Given n variables x_1...x_n and given an integer 1<=k<=n, I'd like to evaluate the k-th elementary symmetric polynomial, as defined -for instance- here:

http://en.wikipedia.org/wiki/Elementary_symmetric_polynomial .

My attempt was to store x=[x_1,...x_n], to define a vector j=[] of length k and then to execute

for j(1)=1:n

    for j(2)=j(i):n
        ...
           for j(n)=j(k-1):n
               e=e + x(j(1))*...*x(j(k));
end...end

How to replace the dots?

Answer 1

[Roger Stafford]

Let v = [x_1,x_2,x_3,...,x_n] be a vector of the values of x_i.

e = sum(prod(nchoosek(v,k),2));