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Ordination graphics Hilltop plots for multiple nonlinear overlays, kernel smoother contouring with optimized or user-controlled smoothing parameter, successional vectors overlay
Weighted Averaging
The simplest yet often effective method of ordination is weighted averaging. The essential operation is the same: a set of pre-assigned species weights (or weights for species groups) are used to calculate scores for sites (sample units). The calculation is a weighted averaging for species or species groups actually present in a sample unit. Weighted averaging used in Federal Manual and numerous ecological indices.
Compare Scores (Compare Ordinations)
Evaluate the similarity of two ordinations, independent of any rotation, reflection, units for axis, and number of dimensions. This is accomplished by evaluating the correlation between the interpoint distances of two ordinations. Squaring this correlation expresses the redundancy between two ordinations. A formal test of the hypothesis of no relationship between the two ordinations is provided by a Mantel test.
Multi-Response Permutation Procedures (MRPP)
MRPP is a non-parametric procedure for testing the hypothesis of no difference between two or more groups of entities. The groups must be a priori. For example, one could compare species composition between burned and unburned plots to test the hypothesis of no treatment effect. Discriminant analysis is a parametric procedure that can be used on the same general class of questions. However, MRPP has the advantage of not requiring assumptions (such as multivariate normality and homogeneity of variances) that are seldom met with ecological community data. Eight distance measures options are available.
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