Selected Publications

  1. Grigsby, M., Di, J., Leroux, A., Zipunnikov, V., Xiao, L., Crainiceanu, C., and Checkley, W.. Novel metrics for growth model selection. Emerging Themes in Epidemiology. 2018; 15(1): 4.
  2. Urbanek, J., Spira, A., Di, J., Leroux, A., Crainiceanu, C., and Zipunnikov, V.. Epidemiology of objectively measured bedtime and chronotype in US adolescents and adults: NHANES 2003 - 2006. Chronobiology International. 2018; 35(3): 416-434.
  3. Varma, V., Dey D., Leroux A., Di, J., Urbanek, J., Xiao, L., and Zipunnikov, V.. Total volume of physical activity: TAC, TLAC, or TAC(\(\lambda\)). Preventive Medicine. 2018; 106: 233-235.
  4. Varma, V., Dey D., Leroux A., Di, J., Urbanek, J., Xiao, L., and Zipunnikov, V.. Re-evaluating the effect of age on physical activity over the lifespan. Preventive Medicine. 2017; 101: 102-108.
  5. Di, J., Li, Y., Friedman, MR., Reddy, S., Surkan, PJ., Shoptaw, S., and Plankey, M.. Determining survey satisficing of online longitudinal survey data in the Multicenter AIDS Cohort Study using a Group-Based Trajectory Analysis. Journal of Medical Internet Research Public Health and Surveillance. 2016; 2 (2): e150.
  6. Di, J., Leroux, A., Urbanek, R., Varadhan, J., Spira, A., Schrack, J., and Zipunnikov, V.. Patterns of sedentary and active time accumulation are associated with mortality in US adults: The NHANES study. bioRxiv: 182337. Under review PLoS ONE.


  1. actigraphy. (R package). Feature extraction for minute level actigraphy data. [Github].
  2. cdHOTS. (R package). Construct and decompose higher order tensorian statistics. [Github]
  3. actigraphy-profiles. (R Shiny App). A visualization tool for displaying minute-level actigrpahy profiles (More features to be online). [Github]