twoway (version 0.6.3)

ladder_power: Find the nearest ladder-of-powers representation of a power transformation

Description

The input power value is rounded to the nearest integer or fractional powers, \(\pm 1/3, 1/2\). The function is presently designed just for display purposes.

Usage

ladder_power(p)

Arguments

p

A numeric power, for use as a transformation of a response, y, of the form \(y^p\), where p=0 is interpreted to mean \(log(y)\)

Value

a named list of two elements: power, the ladder-of-power value, and name, the name for the transformation

Details

In use, the transformation via the ladder of powers usually attaches a minus sign to the transformation when the power < 0, so that the order of the response values are preserved under the transformation. Thus, a result of power = -0.5 is interpreted to mean \(-1 / \sqrt{y}\).

References

Tukey, J. W. (1977). Exploratory Data Analysis, Reading MA: Addison-Wesley.

Examples

# NOT RUN {
ladder_power(0.6)
ladder_power(-0.6)
# }