Individual-based simulation model of annual movement paths for the Darwin's frog (R code and data)

Desprition of the R code I constructed an individual-based simulation model that describes the movement path of an individual Rhinoderma darwinii through 3-month displacement steps. This model was primarily developed to evaluate the age-specific movement behaviour of Darwin's frogs, however, I also used it to provide better estimates (i.e. alleviating for movement censoring) of age-specific annual displacements in the species. I developed several variations of this model through a combination of different random walk sub-models for juveniles and adults: uncorrelated non-stationary random walks (NRW), correlated non-stationary random walks (CRW), and stationary random walks (SRW). The NRW and CRW were modelled as a first-order Markovian process where the location of an individual i in time t depends on its spatial location in t - 1. The NRW is unbiased, i.e., there is no preferred direction in each movement step. In contrast, the CRW includes persistence in the directionality of movement, so there is a correlation between successive step orientations. Finally, the SRW assumes that individuals have an activity centre to which all their spatial locations are related. Related data are provided (y.txt, x.txt and age.txt)

本R代码配套说明：我构建了一款基于个体的模拟模型，用以刻画达尔文蛙（Rhinoderma darwinii）个体以3个月为位移步长的移动路径。该模型最初旨在评估达尔文蛙的年龄特异性移动行为，同时我也借助其对该物种种群的年龄特异性年位移量进行了更精准的估算，即校正移动截尾带来的偏差。我通过为幼体与成体组合不同的随机游走子模型，开发了该模型的多个变体：无关联非平稳随机游走（NRW）、关联非平稳随机游走（CRW）以及平稳随机游走（SRW）。NRW与CRW被建模为一阶马尔可夫过程，即个体i在时刻t的空间位置取决于其在t-1时刻的空间位置。NRW为无偏游走，即每一步移动均无偏好方向；与之相对，CRW保留了移动方向的持续性，因此连续步长的朝向之间存在相关性。最后，SRW假定个体存在一个活动中心，其所有空间位置均围绕该中心分布。相关数据已随附提供（y.txt、x.txt与age.txt）