Transformation Options (t-options)

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The TRANSREG Procedure

Transformation Options (t-options)

The t-options are specified within the parentheses that enclose variables and are listed after a slash.

ALPHA=p
ALP=p: is a new transformation option for use with BOXCOX transformations. The ALPHA= option specifies the alpha for the confidence interval for the power parameter. By default, ALPHA=0.05.
CLL=number-list: is a new transformation option for use with BOXCOX transformations. CLL stands for Convenient Lambda List. When the confidence interval for the power parameter includes one of the values in this list, PROC TRANSREG reports it and can optionally use the convenient power parameter instead of the more optimal power parameter. The default is CLL=1.0 0.0 0.5 -1.0 -0.5 2.0 -2.0 3.0 -3.0. By default, a linear transformation is preferred over log, square root, inverse, inverse square root, quadratic, inverse quadratic, cubic, and inverse cubic. If you specify the CONVENIENT option, then PROC TRANSREG uses the first convenient power parameter in the list that is in the confidence interval. For example, if the optimal power parameter is 0.25 and 0.0 is in the confidence interval but not 1.0, then the convenient power parameter is 0.0.
CONVENIENT
CON: is a new transformation option for use with BOXCOX transformations. The CONVENIENT option specifies that a power parameter from the CLL= list is to be used for the final transformation instead of the LAMBDA= value if a CLL= value is in the confidence interval. See CLL= for more information on the usage of this option.
GEOMETRICMEAN
GEO: is a new transformation option for use with BOXCOX transformations. The GEOMETRICMEAN option specifies that the transformation is to be divided by $\dot{y}^{\lambda - 1}$ where $\dot{y}$ is the geometric mean of the variable to be transformed. This form of the Box-Cox transformation essentially converts the transformation back to original units and hence allows direct comparison of the residual sums of squares for models with different power parameters.
LAMBDA=number-list
LAM=number-list: is a new transformation option for use with BOXCOX transformations. It provides a list of power parameters. The default is LAMBDA=-3 TO 3 BY 0.25. PROC TRANSREG tries each power parameter in the list and picks the best one. However, when CONVENIENT is specified, if there is a convenient power parameter in the confidence interval, it will be chosen instead.
PARAMETER=n
PAR=n: has been enhanced to accept a constant to add to each value of the BOXCOX variable before a Box-Cox transformation. By default, PARAMETER=0 for the BOXCOX transformation.

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