Some preprocessing of the input data by the user may be necessary. Any categorical data to be clustered must first be converted to design-coded numeric variables. Since null data values may bias or invalidate the analysis, they may be replaced, or the listwise deletion option selected to exclude rows with any null values in the preprocessing phase.
Teradata Warehouse Miner automatically builds a single input table from the requested columns of the requested input table. If the user requests more than 30 input columns, the data is unpivoted with additional rows added for the column values. Through this mechanism, any number of columns within a table may be analyzed, and the SQL optimized for a particular Teradata server capability.