Showing papers by "Runze Li published in 2004"
TL;DR: In this paper, two new approaches are proposed for estimating the regression coefficients in a semiparametric model and the asymptotic normality of the resulting estimators is established.
Abstract: Semiparametric regression models are very useful for longitudinal data analysis. The complexity of semiparametric models and the structure of longitudinal data pose new challenges to parametric inferences and model selection that frequently arise from longitudinal data analysis. In this article, two new approaches are proposed for estimating the regression coefficients in a semiparametric model. The asymptotic normality of the resulting estimators is established. An innovative class of variable selection procedures is proposed to select significant variables in the semiparametric models. The proposed procedures are distinguished from others in that they simultaneously select significant variables and estimate unknown parameters. Rates of convergence of the resulting estimators are established. With a proper choice of regularization parameters and penalty functions, the proposed variable selection procedures are shown to perform as well as an oracle estimator. A robust standard error formula is derived usi...
443 citations
TL;DR: Yi et al. as discussed by the authors analyzed data from four forest ecosystems and found that differences among forests in their ability to assimilate CO2 as a function of temperature were attributable to consistent differences in the temperature dependence of photosynthesis and respiration.
Abstract: [1] Future climate change is expected to affect ecosystematmosphere CO2 exchange, particularly through the influence of temperature. To date, however, few studies have shown that differences in the response of net ecosystem CO2 exchange (NEE) to temperature among ecosystems can be explained by differences in the photosynthetic and respiratory processes that compose NEE. Using a new nonparametric statistical model, we analyzed data from four forest ecosystems. We observed that differences among forests in their ability to assimilate CO2 as a function of temperature were attributable to consistent differences in the temperature dependence of photosynthesis and respiration. This observation provides empirical validation of efforts to develop models of NEE from the first-principle relationships between photosynthetic and respiratory processes and climate. Our results also showed that models of seasonal dynamics in NEE that lack specific consideration of the temperature dependence of respiration and photosynthesis are likely to carry significant uncertainties. INDEX TERMS: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 1615 Global Change: Biogeochemical processes (4805); 3307 Meteorology and Atmospheric Dynamics: Boundary layer processes; 3322 Meteorology and Atmospheric Dynamics: Land/atmosphere interactions; 4806 Oceanography: Biological and Chemical: Carbon cycling. Citation: Yi, C., et al. (2004), A nonparametric method for separating photosynthesis and respiration components in CO2 flux measurements, Geophys. Res. Lett., 31, L17107, doi:10.1029/2004GL020490.
33 citations
TL;DR: In this article, a variable selection procedure for the analysis of data obtained from uniform designs is proposed, which is distinguished from the traditional ones in the way that it simultaneously deletes insignificant variables and estimates the coefficients of significant variables.
Abstract: A brief introduction is given to explain the fundamental idea of uniform design and measure of uniformity. A new variable selection procedure is proposed for the analysis of data obtained from uniform designs. This new procedure is distinguished from the traditional ones in the way that it simultaneously deletes insignificant variables and estimates the coefficients of significant variables. This procedure possesses an oracle property, which means that it performs as well as if the true model were known in advance. An example is given to illustrate the application of the uniform design and this variable selection procedure.
30 citations