In addition, Ludi_1 and Ludi_2 also exhibited a very high correlation (R = 0.911). However, the correlation coefficients between Ludi and the other functions, such as PLP and LigScore, were smaller because the master equations that describe the binding free energy used in Ludi are different from those used in the PLP and LigScore functions. In addition, the algorithms vary for the same term in the master equation, such as hydrogen bonding and hydrophobic effect.