1 Department of Biostatistics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
2 Department of Statistics and Operations Research, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
3 Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
4 Department of Computer Science, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
5 Department of Biostatistics, University of Texas MD Anderson Cancer Center, Houston, TX 77230, USA.
6 Department of Statistics, Texas A&M University, College Station, TX 77843, USA.
7 Imaging Genetics Center, Mark and Mary Stevens Institute for Neuroimaging & Informatics, University of Southern California, Los Angeles, CA 90033, USA.