The Category Variable field is used to specify a character variable containing annotation categories. This variable is often obtained from an ontology hierarchy like the Gene Ontology (GO) or from lists of pathways. Multiple categories within a value must be separated by one or two common delimiters, as specified on the General tab. If a row has a blank value for this variable, then that row is excluded from the analysis.All of the variables in the specified annotation data set are displayed in the Available Variables field.
Click to add the highlighted variable to the Category Variable field, as shown below: