y = (x (p_y - q_y))/(p_x - q_x) + (p_x q_y - p_y q_x)/(p_x - q_x) and p_x<=x<=q_x (assuming endpoints (p_x, p_y), (q_x, q_y))

vertex count | 2 edge count | 1

midpoint | (1/2 (p_x + q_x), 1/2 (p_y + q_y)) = (0.5 (p_x + q_x), 0.5 (p_y + q_y)) length | sqrt((p_x - q_x)^2 + (p_y - q_y)^2) slope | (p_y - q_y)/(p_x - q_x) (assuming endpoints (p_x, p_y), (q_x, q_y))