1、Canonical Correspondence Analysis(CCA; ter Braak, 1986,1987) is amultivariate direct gradient analysis method that has become widelyused in ecology. As the name suggests, this method is derived fromcorrespondence analysis, but has been modified to allow environmentaldata to be incorporated into the
2、analysis. It is calculated usingreciprocal averaging form of correspondence analysis. However, at eachcycle of the averaging process, a multiple regression is performed ofthe sample scores on the environmental variables. New site scores arecalculated based on this regression, and then the process is
3、 repeated ,continuing until the scores stabilise. The result is that the axes ofthe final ordination, rather than simply reflecting dimensions of thegreatest variability in the species data, are restricted to the linearcombinations of the environmental variables and the species data. Inthis way thes
4、e two sets of data are then directly relatedRef 1: ter Braak, CJF (1986) Canonical correspondence analysis: A neweigenfactor technique for multivariate direct gradient analysis.Ecology, 67:1167-1179Ref 2: ter Braak, CJF (1987) The analysis of vegetation-environmentrelationships by canonical correspondence analysis. Vegetatio, 64:69-77硡 Kohonen 硣 磬 Kohonen Wij(t)Wij(t) (1) (2) (3)dj(dj (4)jmin(dj) (5)j (6)(2)dj(i)
