The use of mixed effect models with a specific functional form such as the Sigmoidal Mixed Model and the Piecewise Mixed Model (or Changepoint Mixed Model) with abrupt or smooth random change allow the interpretation of the defined parameters to understand longitudinal trajectories. Currently, there are no interface R packages that can easily fit the Sigmoidal Mixed Model allowing the inclusion of covariates or incorporate recent developments to fit the Piecewise Mixed Model with random change. To facilitate the modeling of the Sigmoidal Mixed Model, and Piecewise Mixed Model with abrupt or smooth random change, we have created an R package called nlive. All needed pieces such as functions, covariance matrices, and initials generation were programmed. The package was implemented with recent developments such as the polynomial smooth transition of piecewise mixed model with improved properties over Bacon-Watts, and the stochastic approximation expectation-maximization (SAEM) for efficient estimation. It was designed to help interpretation of the output by providing features such as annotated output, warnings, and graphs. Functionality, including time and convergence, was tested using simulations. We provided a data example to illustrate the package use and output features and interpretation. The package implemented in the R software is available from the Comprehensive R Archive Network (CRAN) at https://CRAN.R-project.org/package=nlive. The nlive package for R fits the Sigmoidal Mixed Model and the Piecewise Mixed: abrupt and smooth. The nlive allows fitting these models with only five mandatory arguments that are intuitive enough to the less sophisticated users.

翻译：在纵向轨迹研究中，采用具有特定函数形式的混合效应模型（如Sigmoidal混合模型和分段混合模型/变点混合模型，其中变点可设置为突变或平滑随机变化）能够通过已定义参数的解释来理解纵向轨迹。目前，尚无集成式R语言包可便捷地拟合允许协变量纳入的Sigmoidal混合模型，或采用最新进展实现含随机变点的分段混合模型拟合。为简化Sigmoidal混合模型及含突变/平滑随机变点的分段混合模型的建模流程，我们开发了名为nlive的R语言包。该包完整编程实现了函数模块、协方差矩阵及初始值生成等基础组件，并整合了多项最新技术进展，包括：具有优于Bacon-Watts模型特性的多项式平滑过渡分段混合模型，以及用于高效参数估计的随机逼近期望最大化算法。为提升输出结果的可解释性，系统设计了带注解的输出报告、运行警告与可视化图形等辅助功能。通过数值模拟验证了该包的时间效率与收敛性能，并基于真实数据示例展示了包的使用方法、输出特性与结果解读。本R语言包已发布在综合R档案网络（CRAN）上，下载地址为https://CRAN.R-project.org/package=nlive。nlive包可拟合突变型与平滑型Sigmoidal混合模型及分段混合模型，用户仅需提供五个高度直观的必填参数即可完成模型构建，特别适合非专业用户使用。