Liu Y Y, Wang Y L
Sci Sin. 1979 Sep;22(9):1082-94.
A stepwise clustering algorithm, a method of multivariate statistical analysis, is suggested in this paper. The algorithm is designed for solving problems connected with stepwise regression. It is efficient not only in handling both continuous and discrete variables, but also in the nonlinear relationships between the variables. The above procedure was used in an attempt to find out the causal association of esophageal cancer with its precursors, i.e. nitrates and nitrites of nitrosamines, some of which are known to be carcinogenic. An analysis has been made of the correlation between esophageal cancer as well as severe epithelial hyperplasia of the esophagus and the concentrations of NO3- and NO2- in the drinking water. The samples used were collected from 495 wells in 49 production brigades of the Yaocun Commune in Linxian County, Honan Province. The result indicates that esophageal cancer is definitely connected with the levels of NO3- (summer) and NO2- (spring) in the drinking water. Severe epithelial hyperplasia is defintely connected with the contents of NO2- and NO3- in the drinking water collected in spring, autumn and winter. Our preliminary analysis shows that the stepwise clustering algorithm is a useful statistical method to be used for medical research.
本文提出了一种逐步聚类算法，这是一种多元统计分析方法。该算法旨在解决与逐步回归相关的问题。它不仅在处理连续变量和离散变量方面效率高，而且在处理变量之间的非线性关系方面也很有效。上述程序被用于试图找出食管癌与其前体物质（即亚硝胺的硝酸盐和亚硝酸盐，其中一些已知具有致癌性）之间的因果关联。对食管癌以及食管严重上皮增生与饮用水中NO3-和NO2-浓度之间的相关性进行了分析。所使用的样本是从河南省林县姚村公社49个生产大队的495口井中采集的。结果表明，食管癌肯定与饮用水中NO3-（夏季）和NO2-（春季）的水平有关。食管严重上皮增生肯定与春、秋、冬三季采集的饮用水中NO2-和NO3-的含量有关。我们的初步分析表明，逐步聚类算法是一种可用于医学研究的有用统计方法。
