twCoefLogitnormCi

Calculates mu and sigma of the logitnormal distribution from lower and upper quantile, i.e. confidence interval.

twCoefLogitnormCi(lower, upper, perc = 0.975, 
    sigmaFac = qnorm(perc), isTransScale = FALSE)

Arguments

lower

value at the lower quantile, i.e. practical minimum

upper

value at the upper quantile, i.e. practical maximum

perc

numeric vector: the probability for which the quantile was specified

sigmaFac

sigmaFac = 2 is 95% sigmaFac = 2.6 is 99% interval

isTransScale

if true lower and upper are already on logit scale

Value

named numeric vector: mu and sigma parameter of the logitnormal distribution.

Author

Thomas Wutzler

See also

logitnorm

Examples

mu = 2
sd = c(1,0.8)
p = 0.99
lower <- l <- qlogitnorm(1 - p, mu, sd )    # p-confidence interval
upper <- u <- qlogitnorm(p, mu, sd )    # p-confidence interval
cf <- twCoefLogitnormCi(lower,upper, perc = p)  
all.equal( cf[,"mu"] , c(mu,mu) )
#> [1] TRUE
all.equal( cf[,"sigma"] , sd )
#> [1] TRUE