CHAPTER 18 Weighted Averaging From: McCune, B. & J. B. Grace Analysis of Ecological Communities. MjM Software Design, Gleneden Beach, Oregon Tables, Figures, and Equations

How it works Matrix A contains abundances of : p species in n sample units Vector of p species weights, w j. Calculate an ordination score v i for each plot i:

A new set of species weights can be calculated from the site scores:

Table Example data matrix with 2 plots  3 species. sp 1sp 2sp 3sum plot A4105 plot B0246 sum434

Table Weights assigned to each species, the weights indicating tolerance of wet to dry sites.

Calculate a moisture score v i for each plot i as an average of the abundances weighted by the moisture indicator values. For example, plot B gets a score of 83.3.

Figure Example of ordination by weighted averaging.