@tomleslie 

Thanks, that was what I was looking for.

@tomleslie Sorry, I forgot to add the '=0' to make the expression an equation.

Thank you for your answer, however, it only solves this particular case. I would be interested in plotting things of the form 'f(x,y)^2+(z-1)^2=0'. Where 'f(x,y)' is a polynomial whose solution is not necessarily parametrizable. Sorry for not explaining this in the original question.

I just found a way of solving this issue. This is the simple solution I found is:

r := rand(1..numelems(A))
rand_in_A := ()-> A[r()]