1. CHAPTER 18 Weighted Averaging From: McCune, B. & J. B. Grace. 2002. Analysis of Ecological Communities. MjM Software Design, Gleneden Beach, Oregon http://www.pcord.comhttp://www.pcord.com Tables, Figures, and Equations

2. 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:

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

4. Table 18.1. Example data matrix with 2 plots  3 species. sp 1sp 2sp 3sum plot A4105 plot B0246 sum434

5. Table 18.2. Weights assigned to each species, the weights indicating tolerance of wet to dry sites.

6. 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.

7. Figure 18.1. Example of ordination by weighted averaging.