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.

ugtransformcommon.png (8876 bytes)

Figure 32.11: 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), y+a\gt
log10(Y+a) a=0 Log10_Y \log_{10}(y+a), y+a\gt
sqrt(Y+a) a=0 Sqrt_Y \sqrt{y+a}, y+a\gt
exp(Y)   Exp_Y \exp(y)
1 / Y   Inv_Y  1/y, 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.

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