Let E = {(x,x)|x ∈ X} ∪ {(x, x)|x ∈ X}.
e is the space of event of the classification problem, and For classifier g f on space e, its loss function is x 2 =x 1 and g f (x 1 , x 2 ) = +1 0 otherwise the expected risk R vote (f ) for the voting problem is equivalent to the expected risk R class (g f ) for the classification problem.