[1] Univ Calif San Francisco, Grad Program Bioinformat & Computat Biol, San Francisco, CA 94143 USA
[2] Univ Calif San Francisco, Calif Inst Quantitat Biosci, San Francisco, CA 94143 USA
[3] Univ New Mexico, Dept Math & Stat, Albuquerque, NM 87131 USA
[4] Univ Calif San Francisco, Dept Bioengn & Therapeut Sci, San Francisco, CA 94143 USA