Creating indicators on variables

Indicator is the term PRIMER uses for a factor defined on the variables not on the samples. It is convenient to use a separate term because ‘factor’ has a well-established statistical meaning (e.g. in ANOVA-type layouts), and refers to structures defined on samples, not on variables. Indicators are less used than factors in practice, though they have a useful role in selecting or removing subsets of variables for the analysis of samples (e.g. only analyse the metals data rather than all environmental variables; only analyse zooplankton, omitting phytoplankton species etc). Adding and manipulating indicators, however, proceeds exactly as for factors, with parallel choices of Add, Combine, Rename, Reorder, Delete, Key and Import from the Indicators sheet produced by Edit>Indicators.

A simple example is seen in the Tasmania copepods(.pri) data sheet. Edit>Indicators (also on the right click menu when the cursor is over the data sheet) shows the indicator ID?, which records whether each taxon has been identified (1) or is an undetermined specimen (0). The ID? indicator is also shown above (far right) in the Excel format of this file.