As mentioned above, the importance of each feature is rated according to its rank in the mRMR analysis. The next step is to determine which features should be selected as the optimal feature set for our drug-target predictor. Here the IFS (Incremental Feature Selection) procedure is used to solve the problem. Each feature in the mRMR feature list was added one by one, and N different feature sets are obtained if the total feature number is N, while the i-th feature set is: