Summary of Research
Early in my academic career, I worked on times series analysis. In the past few years, my primary research interest is in spatial statistics (which includes the spatio-temporal case), and the applications of spatial statistics to environmental, agricultural and natural resources sciences. My research has been supported by the National Science Foundation (
DMS-0405782, 2004-2007,
DMS-0706835, 2007-2010) and other sources. The research problems in spatial statistics that I have studied are roughly grouped as follows.
- Spatial Generalized Linear Mixed Models
- Infill Asymptotics
- Multivariate Spatial Statistics
- Methods for analyzing massive spatial data
Some Ongoing Projects
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Approximate inferences for massive spatial or spatio-temporal data: The sample size of a spatial sample may be extremely large and this is usually the case with spatio-temporal data. Currently, I am studying some approximate approaches that are computationally feasible and yet yields no or little loss of efficiency compared with that of the MLE.
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Bias correction for the approximate inferences for spatio-temporal data: Recent years have seen the development of new space-time covariance functions. Estimation of parameters in the covariance function can be a computational burden especially when the sample size is extremely large. I am working on an approach to employ misspecified but simpler space-time covariance functions and then adjust for the bias resulted from the misspecification. The adjustment is based on asymptotic results.
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Stationary processes with skewed marginal distributions: In many applications, spatial data are skewed (and often right skewed as in many environmental studies). Sometimes directly modeling the skewed process is preferable to the transformation method.
Collaborative Research
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I have collaborated with several agricultural scientists on various projects ranging from crop insurance, precision agriculture, plant pathology and natural resources. Many of the projects provided motivating spatial data.
- My collaborators at Purdue University are from several departments and centers: Forestry and Natural Resources, Agronomy, Agricultural and Biological Engineering, Earth and Atmospheric Sciences, Center for Environment and Purdue Climate Change Research Center.
Statistical Consulting
I have more than 10 years of experience in statistical consulting, providing statistical advices on experimental design, data analysis, model selection and diagnosis, and various statistical issues.