Bioinformatics Research Center, North Carolina State University, Ricks Hall, 1 Lampe Dr., Raleigh, NC 27607, USA, Division of Bioinformatics, Omicsoft Inc., 200 Cascade Pointe Lane, Suite 101, Cary, NC 27513, USA, Department of Statistics, North Carolina State University, Ricks Hall, 1 Lampe Dr., Raleigh, NC 27607, USA and Department of Statistics, National Cheng-Kung University, No.1, University Road, Tainan 701, TaiwanBioinformatics Research Center, North Carolina State University, Ricks Hall, 1 Lampe Dr., Raleigh, NC 27607, USA, Division of Bioinformatics, Omicsoft Inc., 200 Cascade Pointe Lane, Suite 101, Cary, NC 27513, USA, Department of Statistics, North Carolina State University, Ricks Hall, 1 Lampe Dr., Raleigh, NC 27607, USA and Department of Statistics, National Cheng-Kung University, No.1, University Road, Tainan 701, Taiwan.