Table of Common Transformations

There are many types of associations that you may encounter. This table lists the most common and summarizes the way each variable may be transformed. The list is not exhaustive, there are other possible transformations.

Logarithmic
General algebraic equation
y = lnx	

Take the log (natural or base 10) of the explanatory variable, x.	
	
Exponential
General algebraic equation
y = aex	

Take the log of the explanatory variable, x.	
	
Quadratic
General algebraic equation
y = ax2 + bx + c	

Take the square root of the explanatory variable, x.	
	
Power
General algebraic equation
y = axb	

Take the log of both variables.	
	
Complex
More than one type of equation may be used to describe the association.	

Break the data into two or more functions and apply the appropriate transformations	

Notice that the transformations exponential, quadratic, and power look very similar. Check the coefficient of determination after transformation to see which may be the best model.