The statistical modelling of integer-valued extremes such as large avalanche counts has received less attention than their continuous counterparts in the extreme value theory (EVT) literature. One approach to moving from continuous to discrete extremes is to model threshold exceedances of integer random variables by the discrete version of the generalized Pareto distribution. Still, the optimal threshold selection that defines exceedances remains a problematic issue. Moreover, within a regression framework, the treatment of the many data points (those below the chosen threshold) is either ignored or decoupled from extremes. Considering these issues, we extend the idea of using a smooth transition between the two tails (lower and upper) to force large and small discrete extreme values to comply with EVT. In the case of zero inflation, we also develop models with an additional parameter. To incorporate covariates, we extend the Generalized Additive Models (GAM) framework to discrete extreme responses. In the GAM forms, the parameters of our proposed models are quantified as a function of covariates. The maximum likelihood estimation procedure is implemented for estimation purposes. With the advantage of bypassing the threshold selection step, our findings indicate that the proposed models are more flexible and robust than competing models (i.e. discrete generalized Pareto distribution and Poisson distribution).
翻译:在极端价值理论(EVT)文献中,对诸如大型雪崩计等全值极端的统计建模不如对极值理论(EVT)文献中连续的对等者受到重视。从连续的极端到离散的极端的一个办法就是通过通用Pareto分布的离散版本模拟整数随机变量的临界超值。不过,界定超值的最佳阈值选择仍然是一个问题。此外,在回归框架内,许多数据点(低于所选阈值)的处理要么被忽略,要么与极端脱钩。考虑到这些问题,我们扩大了使用两个尾巴(低端和上端)之间平稳过渡的想法,以迫使大、小的离散极端值遵守EVT。在零通货膨胀的情况下,我们还开发了带有额外参数的模型。要纳入共变式,我们将通用Additive模型(GAM)框架扩大到离散的极端反应。在GAM表格中,我们拟议模型的参数被量化为共差函数。我们采用最大的可能性估计程序是为了估计目的。在比较性临界值的基础上,采用最强的分布模型。在比较灵活和离差的模型中,显示比分散模型的优势。