Transformation

The Transformation dialog allows you to perform functions on variables in your data set, then use these transformed variables in Linear Regression or Analysis of Variance formulas. This dialog is opened through the Transformation dialog, which allows you to perform functions on variables in your data set and then use these transformed variables in Linear Regression or Analysis of Variance formulas. This dialog is opened through the Create Formula page of the Linear Regression or Analysis of Variance dialog.

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The Transformation dialog has the following options:

Variable

Variables listed in the formula dialog are displayed in the Choose Variables field. To select more than one variable, hold down the CTRL key. After variable selection, select a function to apply to the selection. The transformed variables are displayed in the New Variables field. Click Add to add the transformed variables to the Choose Variables field.

Function

Click on a button in this group to apply a transformation to the selected variables. The eight buttons perform the transformations, Absolute: abs(x) for absolute value, Exp: exp(x) for exponential, Log: log(x) for natural log, Log10: log10(x) for log base 10, Sq. Root: sqrt(x) for square root, Reciprocal: x^(-1) for reciprocal, Quadratic: x^2 for quadratic, Cubic: x^3 for cubic.

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A list of variables in the formula dialog is required to open the transformation dialog. When the transformation dialog is up, the model and the Formula dialogs are disabled until OK or Cancel is clicked. Select variable(s), select a function, then add the new variable to the list. The new variables list is sent back to the formula dialog after you click on OK.