Canonical Correspondence Analysis
Biplot This button presents a grid of the coordinates of the tip of the environmental
variable vectors used in the ordination biplots to show species relationships to the
environmental variable (see
Inter This button presents the correlation between the environmental variables and
the site (sample) scores calculated using the weighted average of the species. It is
termed the Inter set correlation.
Intra This button presents the correlation between the environmental variables and
the site (sample) scores calculated using the regression of the environmental
variables with the site scores derived from the species. It is termed the Inter set
correlation. It is always larger than the intra set correlation.
These results can be printed or exported from the File menu and copied from the Edit
Export Active Grid
Monte Carlo Simulations
Monte Carlo randomization tests are only undertaken if selected from the
Randomization drop down menu. This menu allows you to select 100, 1000, and
10000 trials. It is a good idea to initially run only a hundred simulations as this
procedure can take a long time if you have a large data set.
For each simulation the order of the samples in the sample species array is randomly
shuffled and the Eigenvectors calculated as usual. By shuffling the order of the
samples we are breaking the correlation between the environmental variables and the
species. Thus there will not be any relationship. The probability measure given in the
Monte Carlo output grid is the probability that an Eigenvalue as large as that observed
could have occurred by chance. Also given in the table is the largest and smallest
Eigenvalues observed and the mean Eigenvalue. The calculations are only undertaken
for the 3 axes with the largest Eigenvalues as it is unlikely that you will have
significant variation explained by subsequent axes.
Copyright 2004 PISCES Conservation Ltd