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|Home MathPack DataTable Nominal and Ordinal Data|
|See also: Using TDataTable, NominalID, MScaleType, OrdinalOfNominalID, ElemNominal, AddNominalID|
Nominal and Ordinal Data
When dealing with measurement data we have to differentiate between nominal, ordinal, interval and ratio-scaled data. From a mere technical viewpoint interval and ratio-scaled variables are floating point values, while nominal and ordinal variables represent some kind of "enumerated" values (comparable to user-defined types in programming).
In order to make it easier to work with nominal and ordinal data, TDataTable provides a simple way to define the measurement scale of a variable and to specify the enumerated values by assigning short strings to the nominal/ordinal values stored in the data matrix.
Nominal and ordinal values are always stored as rounded floating point values and may take any (integer) value. However the values from 1 to DT_MaxNominalIDs may be represented by short texts which can be specified by using the array property NominalID. It is therefore recommended always to use values between 1 and DT_MaxNominalIDs for specifying nominal or ordinal data.