Canonical Correspondence Analysis

36

"northerliness" and "easterliness" as follows:

easterliness = cos(aspect)

easterliness = sin(aspect)

Northerliness will take values close to 1 if the aspect is generally northward, close to  

1 if the aspect is southward, and close to 0 if the aspect is either east or west.

Easterliness behaves similarly, except that values close to 1 represent east facing

slopes.

Another approach is to use 

dummy variables

 e.g. N, NE, E, SE, S, SW, W, NW. This

approach has the additional advantage of allowing flat surfaces (i.e. no aspect) to

have a category.

The day of the year is circular because early January will have low values, and late

December will have high values, yet the climates at the two times will be similar. As

with compass direction one approach is to construct dummy variables Winter, Spring,

Summer and Autumn. If sampling occurred over a limited number of months the

Julian date can be used as a variable.

For more advanced work with circular or repeating variables Pisces produce a

dedicated package  Axis , more details of which are available here.

7.8

Species Scores

This grid gives the score for each species for each axis and are the values that are

plotted to form the species ordination (see 

Ordination Plot

).

These results can be printed or exported from the File menu and copied from the Edit

menu. See 

Export Active Grid

Copyright 2004  PISCES Conservation Ltd