Water Environment Fuzzy Comprehensive Evaluation Based on Improved Set Pair Analysis (SPA)

Set pair analysis (SPA) is a method for the application on analysis of risks and project decision evaluation. This method combines qualitative analysis and quantitative analysis. The previous SPA study only focused on three ranks evaluation. This paper presents an improved SPA method utilizing original relation degree malleability of SPA, and extends it to five ranks evaluation. The improved method can depict identity, discrepancy and contrary in more detail. In addition, this study combines fuzzy comprehensive evaluation method to evaluate four main factors of surface water environment, instead of the discussion of i⁺, i^-, j⁺, j^- coefficient. It not only obtains evaluation result but also obtains probability distribution of each rank. In this paper, we apply the method to factual example and compare the results with synthesis index method, and gray associated analysis method. We conclude that the improved method can represent the true state of the object with extensive engineering application value.