Z-Score - Teradata Warehouse Miner

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 generally more useful in data mining than 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.

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.

For the Derive transformation, the outputname parameter controls the naming of the transformed output column.

database

The database containing the input table.

tablename

The name of the table to be transformed.

vartran

This parameter is required to run a variable transformation. The vartran parameter is always enclosed in single quotes.

zscore

The parameter that identifies the type of transformation being performed.

General Parameters (separated by semi-colons)

datatype

For all transformation types, the datatype parameter is used to cast the column to a desired database data type provided it is compatible with the transformed data.

The allowed output types include:

• byteint
• char
• date
• decimal
• float
• integer
• smallint
• time
• timestamp
• varchar
• bigint
• number

fallback

When set to true, this parameter requests a mirrored copy of the output table in the Teradata Database when outputstyle=table.

gensqlonly

When set to true, the SQL for the requested transformations is returned as a result set but not executed. When this parameter is not specified or is set to false, the SQL is executed but not returned.

indexcolumns

When set to true, requests the output table contain the index columns when outputstyle=table.

indexunique

When set to 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 set to true, requests an output table that may contain duplicate rows when outputstyle=table.

noindex

When set to 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 that will contain the resulting output table when outputstyle=table or view.

outputstyle

The allowed output styles are:

• select
• table
• view

If outputstyle is not specified, the function generates a SELECT statement and does not create a table or view.

outputstyle={select||table||view}

outputtablename

The name of the output table when outputstyle=table or view.

whereclause

Requests the generated SQL contain the given WHERE clause in appropriate places in the generated SQL. This is independent of the output style requested.

Examples

Examples in this section show how to use Z-Score. These examples assume that the td_analyze function has been installed in a database named twm.

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. keycolumns 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);');