Select the transformation for selected attribute from the dropdown list, and enter any necessary values. For example, if you select LN(x + a)
, you must specify a value for a
. Note the restrictions on scheme values; for example, if you select LN(x + a)
, the value of a
must be such that x + a
> 0 for all values of the attribute.
The wizard displays statistics for the Original values and the Transformed values. Initially, both sets of statistics are the same. To see statistics for transformed values, select a transformation and click Refresh.
When you are satisfied with the scheme definition, click OK to apply the scheme. You can click Cancel to cancel the scheme selection.
You can select one of the following predefined schemes:
EXP(x)
, where x
<= 70 (Oracle database limit)1 / EXP(AVG(x) - x)
, where AVG(x) - x
<= 70 (Oracle database limit)LN(x + a)
, where a
is a user-supplied numeric constant and x + a
> 0; LN is natural logarithm.
Use this scheme when you are dealing with large numbers; this transformation makes the distribution more like a normal distribution.
LN((x - a) / (b - x))
, where a
and b
are user-supplied numeric constants and (x - a) / (b - x)
> 0; LN
is the natural logarithm. LOG(10, x + a)
, where a
is a user-supplied numeric constant and x + a
> 0; LOG(10, z)
is the logarithm to the base 10 of z
.
Use this scheme when you are dealing with large numbers; this transformation makes the distribution more like a normal distribution.
SQRT(x)
, where x
>= 0
Use this function to linearize a distribution.
Note: The functions (EXP, LN, etc.) in the schemes use the notation of the SQL functions; for definitions, see Numeric Functions in Schemes.
To see the effect of the transformation immediately, click Refresh.
Click OK to select the scheme.
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