3.2 The power family of transformations

Stretching the axis differentially.

p =	2	1	$\frac{1}{2}$	$\frac{1}{3}$	$-\frac{1}{2}$	-1
	z2	z	$\sqrt{z}$	${}^3\sqrt{z}$	$\frac{1}{\sqrt{z}}$	$\frac{1}{z}$

Unfortunately does not include ln.

Fix up: consider

$$\frac{z^p - 1}{p}.$$

Take the limit as $p \rightarrow 0$ and you get ln(z).

Need to know the shape of these curves.

The most commonly used is probably the log-transform.

Reasons:

Good interpretability in terms of percentage changes.

Turns multiplicative relationships into additive ones.