Likelihood ratio test, rankcorrelationanalysis and principal component analysis were used to investigate the optimal model of function and the index system.
似然比检验、秩相关分析、主成分分析等方法相继用于研究函数的最适模型和指标体系。
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Rankcorrelation analyses show that all of the runoff sequence change with tendency, and the sudden change appeared in 1948, as concluded by order cluster analysis method.