Variable Transformations

Common Transformations

Figure 32.11 shows the transformations that are available when you select Common from the Family list. Equations for these transformations are given in Table 32.1.

Figure 32.11: Common Transformations

Common Transformations


Table 32.1: Description of Common Transformations

 

Default

Name of

 

Transformation

Parameter

New Variable

Equation

log(Y+a)

$a=0$

Log_Y

$\log (Y+a), \quad Y+a>0$

log10(Y+a)

$a=0$

Log10_Y

$\log _{10}(Y+a), \quad Y+a>0$

sqrt(Y+a)

$a=0$

Sqrt_Y

$\sqrt {Y+a}, \quad Y+a>0$

exp(Y)

 

Exp_Y

$\exp (Y)$

1 / Y

 

Inv_Y

$ 1/Y, \quad Y\neq 0$

Y * Y

 

Squared_Y

$Y^2$


The logarithmic transformations are often used when the scale of the data range exceeds an order of magnitude. The square root transformation is often used when your data are counts. The inverse transformation is often used to transform waiting times.