Sabre

TRANSFORM

Sabre manual

Syntax:
TRANSFORM variable function var1 or
TRANSFORM variable var1 ^ number or
TRANSFORM variable var1 operator var2 or
TRANSFORM variable var1 operator number
where variable is the name of the transformed variable, var1 & var2 are explanatory variables, number is a real number, function is either exp or log and operator is either*, /, + or -.

Purpose:
The TRANSFORM command performs simple data transformations and also forms interactions between variables and/or factors.

Note that interactions are formed simply by using the multiplication operator on two variables or factors (no other type of transformation can have a factor as an argument). Interactions between var1 with n1 levels and var2 with n2 levels may be of the form:

variable by variable (interaction term is a variable)
non-zero variable by factor (interaction term is a pseudo factor with n2 levels)
factor by non-zero variable (interaction term is a pseudo factor with n1 levels)
factor by factor (interaction term is a factor with n1*n2 levels)

The number of levels in an interaction may be obtained by issuing the DISPLAY VARIABLES command.