logit function

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()

Returns

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)

expit(-1.09)

logitNormInfo(logit(0.25), sd = 0.1)

logitNormInfo(logit(1, 0, 10), sd = 1, low = 0, high = 10)