I use PolynomialExpansion to convert one vector to 2-degree vector. I am confused about the result of following. As my understanding, the 2 degrees vector should contain 4 1's, not sure how the 5 1's come from. I think it supposed to be (x1,x2,x3) *(x1,x2,x3) = (x1*x1, x1*x2, x1*x3, x2*x1,x2*x2, x2*x3, x3*x1, x3*x2,x3*x3)
(3,[0,2],[1.0,1.0]) --> (9,[0,1,5,6,8],[1.0,1.0,1.0,1.0,1.0])| -- Best Regards Jeff Zhang