logit and inverse logit (expit) functions

logit(x, low = 0, high = 1)

expit(alpha, low = 0, high = 1)

logitNormInfo(mean = 0, sd = 1, low = 0, high = 1, abs.tol = 1e-06, ...)

probitNormInfo(mean = 0, sd = 1, low = 0, high = 1, abs.tol = 1e-06, ...)

Arguments

x

Input value(s) in range [low,high] to translate -Inf to Inf

low

Lowest value in the range

high

Highest value in the range

alpha

Infinite value(s) to translate to range of [low, high]

mean

logit-scale mean

sd

logit-scale standard deviation

abs.tol

absolute accuracy requested.

...

other parameters passed to integrate()

Value

values from logit and expit

Details

logit is given by:

logit(p) = -log(1/p-1)

where:

p = x-low/high-low

expit is given by:

expit(p, low, high) = (high-low)/(1+exp(-alpha)) + low

The logitNormInfo() gives the mean, variance and coefficient of variability on the untransformed scale.

Examples


logit(0.25)
#> [1] -1.098612

expit(-1.09)
#> [1] 0.2516183

logitNormInfo(logit(0.25),sd=0.1)
#>         mean          var           cv 
#> 0.2504672899 0.0003515538 0.0748591440 

logitNormInfo(logit(1,0,10), sd=1, low=0, high=10)
#>      mean       var        cv 
#> 1.3386966 1.2662276 0.8405697