Liang Shengde, Banerjee Sudipto, Carlin Bradley P
MMC 303, School of Public Health, University of Minnesota, Minneapolis, Minnesota 55455-0392, USA.
Biometrics. 2009 Dec;65(4):1243-53. doi: 10.1111/j.1541-0420.2009.01203.x.
In many applications involving geographically indexed data, interest focuses on identifying regions of rapid change in the spatial surface, or the related problem of the construction or testing of boundaries separating regions with markedly different observed values of the spatial variable. This process is often referred to in the literature as boundary analysis or wombling. Recent developments in hierarchical models for point-referenced (geostatistical) and areal (lattice) data have led to corresponding statistical wombling methods, but there does not appear to be any literature on the subject in the point-process case, where the locations themselves are assumed to be random and likelihood evaluation is notoriously difficult. We extend existing point-level and areal wombling tools to this case, obtaining full posterior inference for multivariate spatial random effects that, when mapped, can help suggest spatial covariates still missing from the model. In the areal case we can also construct wombled maps showing significant boundaries in the fitted intensity surface, while the point-referenced formulation permits testing the significance of a postulated boundary. In the computationally demanding point-referenced case, our algorithm combines Monte Carlo approximants to the likelihood with a predictive process step to reduce the dimension of the problem to a manageable size. We apply these techniques to an analysis of colorectal and prostate cancer data from the northern half of Minnesota, where a key substantive concern is possible similarities in their spatial patterns, and whether they are affected by each patient's distance to facilities likely to offer helpful cancer screening options.
在许多涉及地理索引数据的应用中,关注点集中在识别空间表面快速变化的区域,或者是构建或检验分隔具有明显不同空间变量观测值区域的边界这一相关问题。在文献中,这个过程通常被称为边界分析或沃姆布林分析。针对点参考(地理统计)数据和面数据(格网数据)的分层模型的最新发展,已经产生了相应的统计沃姆布林方法,但在点过程情形下,似乎没有关于这个主题的任何文献,在这种情形中,位置本身被假定为随机的,并且似然评估非常困难。我们将现有的点级和面级沃姆布林工具扩展到这种情形,得到多元空间随机效应的完整后验推断,当进行映射时,这有助于指出模型中仍然缺失的空间协变量。在面数据情形下,我们还可以构建显示拟合强度表面中显著边界的沃姆布林地图,而点参考公式允许检验假定边界的显著性。在计算要求较高的点参考情形下,我们的算法将似然的蒙特卡罗近似与预测过程步骤相结合,以将问题的维度降低到可管理的大小。我们将这些技术应用于对明尼苏达州北半部的结直肠癌和前列腺癌数据的分析,其中一个关键的实质性问题是它们空间模式中可能存在的相似性,以及它们是否受到每位患者到可能提供有用癌症筛查选项的设施的距离的影响。