Used to create a single key from two hierarchical factors.
define.key(data, upper = "", lower = "",
upper.levels = "Upper.Levels", lower.levels = "Lower.Levels")
A data frame
A character. Indicates a factor in the data frame which corresponds to the factor with the higher number of levels (typically SOC variable)
A character. Indicates a factor in the data frame which corresponds to the factor with the lower number of levels (typically PT variable)
A character. The label to be displayed in the table for the upper terms
A character. The label to be displayed in the table for the lower terms
Used internally by report.quali.hlev