Nominal Seriation

Nominal seriation is a generalization of occurrence seriation. Instead of categorizing each feature into two classes (present or absent), the technique allows any number of classes. If the classes are numbered, it does not imply that items should be seriated in order of their class number (see Classed Data). The seriation technique can be set in the Seriations table.

Nominal seriation is used when only the presence or absence of feature classes is known and metric data is unavailable. For nominal seriation OptiPath uses the Optimal Path Seriation model with Hamming distance.

In nominal seriation, careful thought should be put into setting the feature parameters Earlier, Later, Blanks and Zeroes appropriately - see Setting the Earlier, Later, Blanks, Zeroes and Transition Parameters. When you choose the Nominal seriation Technique, OptiPath automatically sets these parameters. To change them you must first select the Custom Technique.

OptiPath allows you to simultaneously treat some features as classifications and others as occurrences/absences or as measured data. See Data in the Features window.