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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 ratioscaled data. From a mere technical viewpoint interval and ratioscaled variables are floating point values, while nominal and ordinal variables represent some kind of "enumerated" values (comparable to userdefined 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.
