nth_element on a vector of structs c++

I want to run the c++ function nth_element on a vector of structs but I'm not sure how to get it to work.

Here is my current code:

struct Point {
    int x, y, color;
};

bool compareByY (const Point &a, const Point &b)
{
    return a.y < b.y;
}

nth_element(points.begin(), points.size() +  points.size()/2, points.end(), compareByY);