1. Department of Biostatistics, School of Public Health, Yale University, New Haven, CT, U.S.A.
2. Department of Genetics, School of Medicine, Yale University, New Haven, CT, U.S.A.
3. Center for Medical Informatics, School of Medicine, Yale University, New Haven, CT, U.S.A.
4. Department of Computer Science, Yale University, New Haven, CT, U.S.A.