Purpose
Similar to a Sigmoid transformation, a Z-Score transformation provides rescaling of continuous numeric data in a more sophisticated way than a Rescaling transformation. In a Z-Score transformation, a numeric column is transformed into its Z-score based on the mean value and standard deviation of the data in the column. It transforms each column value into the number of standard deviations from the mean value of the column. This non-linear transformation is useful in data mining rather than in a linear Rescaling transformation.
The Z-Score transformation supports both numeric and date type input data.
Refer to Teradata Warehouse Miner User Guide, Volume 2, ADS Generation, Release 5.4.2, B035-2301 for the formulas associated with the Z-Score function.
Syntax
call twm. td_analyze('vartran','database=twm_source;tablename=twm_customer;General Parameters;zscore=columns (values),datatype (integer);');Required Parameters
- columns
- Controls the name of the output (transformed) column and its data type. The columns parameter is required by all transformations except Derive. A separate transformation is performed for each column in the list. If a column name is followed by a forward slash and a name, the name after the slash becomes the name of the transformed column in the resultant output table. Otherwise the column name is used as the output column name.
- database
- The database containing the input table.
- tablename
- The input table to build a predictive model from.
- vartran
- Required to run a variable transformation. Enclose the 'vartran' parameter in single quotes.
- zscore
- Identifies the type of transformation being performed.
Optional Parameters
- datatype
- For all transformation types, the datatype casts the column to a desired database data type provided it is compatible with the transformed data. Allowed output types include:
- byteint
- char
- date
- decimal
- float
- integer
- smallint
- time
- timestamp
- varchar
- bigint
- number
- fallback
- When true, requests a mirrored copy of the output table in the Teradata Database when outputstyle=table.
- gensqlonly
- When true, the SQL for the requested transformations is returned as a result set but not executed. When not specified or set to false, the SQL is executed but not returned.
- indexcolumns
- When true, requests the output table contain the index columns when outputstyle=table.
- indexunique
- When true, requests the output table contain a unique primary index when outputstyle=table.
- keycolumns
- When null replacement is requested, either via a Null Replacement transformation or in combination with a Bin Code, Derive, Design Code, Recode, Rescale, Sigmoid, or Z Score transformation, the keycolumns parameter must be specified. The column or columns listed must form a unique key into the input and output table of the transformation.
- lockingclause
-
Requests the generated SQL contain the given locking clause in the appropriate location depending on the output style.
An example of a locking clause when the output style defaults to select is:
LOCKING mydb.mytable FOR ACCESS;
- multiset
- When true, requests an output table that can contain duplicate rows when outputstyle=table.
- noindex
- When true, requests the output table contain no index columns when outputstyle=table.
- nullstyle
-
Data types supported by various nullstyle parameters are:
Data Type Description Example literal,value numeric, character, and date nullstyle (literal,value) mean numeric and date nullstyle (mean) median numeric and date nullstyle (median) medianwithoutaveraging any supported data type nullstyle (medianwithoutaveraging) mode any supported date type nullstyle (mode) imputed,table any supported data type nullstyle (imputed,tablename) If date values are entered, the keyword DATE must precede the date value, which should not be enclosed in single quotes.
- outputdatabase
- The database containing the resulting output table when outputstyle=table or view.
- outputstyle
- Allowed output styles are:
- select
- table
- view
- outputtablename
- The name of the output table when outputstyle=table or view.
- overwrite
-
When overwrite is set to true (default), the output tables are dropped before creating new ones.
- whereclause
- Requests the generated SQL containing the given WHERE clause in appropriate places in the generated SQL. This is independent of the output style requested.
Examples
These examples show how to use Z-Score. To execute the provided examples, the td_analyze function must be installed in a database called twm and the Teradata Warehouse Miner tutorial data must be installed in the twm_source database.
The following example demonstrates the Z-Score transformation.
call twm.td_analyze('vartran','database=twm_source;tablename=twm_customer;zscore=columns(age,income/inc),datatype(integer);');
The following example demonstrates combined null replacement. The keycolumns parameter must be included as a general parameter when null value replacement is performed.
call twm.td_analyze('vartran','database=twm_source;tablename=twm_customer;keycolumns=cust_id;zscore=nullstyle(literal,0),columns(age,income);');