gtools (version 3.9.5)

logit: Generalized logit and inverse logit function

Description

Compute generalized logit and generalized inverse logit functions.

Usage

logit(x, min = 0, max = 1)
inv.logit(x, min = 0, max = 1)

Value

Transformed value(s).

Arguments

x

value(s) to be transformed

min

Lower end of logit interval

max

Upper end of logit interval

Author

Gregory R. Warnes

Details

The generalized logit function takes values on [min, max] and transforms them to span [-Inf,Inf] it is defined as:

$$y = log(\frac{p}{(1-p)})$$

where

$$p=\frac{(x-min)}{(max-min)}$$

The generalized inverse logit function provides the inverse transformation:

$$x = p' (max-min) + min$$

where

$$p'=\frac{exp(y)}{(1+exp(y))}$$

See Also

logit

Examples

x <- seq(0, 10, by = 0.25)
xt <- logit(x, min = 0, max = 10)
cbind(x, xt)

y <- inv.logit(xt, min = 0, max = 10)
cbind(x, xt, y)