37

ECOM II

7.9

Variance & Eigenvalues

For both Redundancy Analysis and Canonical Correspondence Analysis this tab

presents tabulated data for the eigenvalues of each axis and the amount of variance

present in the original data that is accounted for by the axis. It also gives summary

information on your data set.

The total variance or what is more strictly termed inertia is the sum of the canonical

and non canonical Eigen values.

The output is explained below.

Number of sites   This is the number of columns in the Sample/Species array loaded

as the biological file. It may be the number of transects, quadrats, pitfall traps etc.

Number of species   This is the number of rows in the Sample/Species array loaded

as the biological file. It is the total number of taxa in the data set.

Number of environmental variables   This is the number of rows in the

Environmental array loaded as the biological file. It is the total number of taxa in the

data set.

Number of canonical axes   This is the number of axes that can be related to

environmental variables.

Number of non canonical axes   This is the number of axes that hold the residual

variance unexplained by a linear combination of the environmental variables.

Total variance   This is the sum of the variance explained by the canonical and non 

canonical eigenvalues.

Canonical Eigenvalues   These are the eigenvalues for the canonical axes.

% variance explained   This is the amount of the total variance in the data that is

explained by each of the canonical axes.

Cumulative % variance   This is the sum total of the variance explained by the

addition of each new canonical axis.

Multiple correlation species/environment scores   The analysis produces scores

for each site based on either their environmental variables or species composition.

This row gives, for each canonical axis, the correlation between these two scores for

all the sites. The value presented is the multiple correlation coefficient produced by a

Copyright 2004  PISCES Conservation Ltd