This paper presents a novel semiparametric joint model for multivariate longitudinal and survival data (SJMLS) by relaxing the normality assumption of the longitudinal outcomes, leaving the baseline hazard functions unspecified and allowing the history of the longitudinal response having an effect on the risk of dropout. Using Bayesian penalized splines to approximate the unspecified baseline hazard function and combining the Gibbs sampler and the Metropolis-Hastings algorithm, we propose a Bayesian Lasso (BLasso) method to simultaneously estimate unknown parameters and select important covariates in SJMLS. Simulation studies are conducted to investigate the finite sample performance of the proposed techniques. An example from the International Breast Cancer Study Group (IBCSG) is used to illustrate the proposed methodologies.
Based on the double penalized estimation method, a new variable selection procedure is proposed for partially linear models with longitudinal data. The proposed procedure can avoid the effects of the nonparametric estimator on the variable selection for the parameters components. Under some regularity conditions, the rate of convergence and asymptotic normality of the resulting estimators are established. In addition, to improve efficiency for regression coefficients, the estimation of the working covariance matrix is involved in the proposed iterative algorithm. Some simulation studies are carried out to demonstrate that the proposed method performs well.
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