Transform a between bound and unbounded scales.

Usage

logit(x, lower_bound = 0, upper_bound = 1, base = exp(1))

expit(x, lower_bound = 0, upper_bound = 1, base = exp(1))

Arguments

x: Value to be rescaled.
lower_bound: Lower bound of x; defaults to 0.
upper_bound: Upper bound of x; defaults to 1.
base: Base used for log-transform, defaults to exp(1) = e

Details

logit() will transform a value on a bound scale to an unbound scale, while expit() performs the reverse transformation. Values at the lower/upper bounds correspond to -Inf/Inf on the unbounded scale. Uses the natural base, e, by default, but other bases can be passed to the parameter base.

Examples

# unbound vector of values bound between [0, 1]
myvec <- seq(0, 10, 1)/10
logit(myvec)
#>  [1]       -Inf -2.1972246 -1.3862944 -0.8472979 -0.4054651  0.0000000
#>  [7]  0.4054651  0.8472979  1.3862944  2.1972246        Inf

# unbound vector of values between [100, 200]
myvec <- seq(100, 200, 10)
logit(myvec, lower_bound = 100, upper_bound = 200)
#>  [1]       -Inf -2.1972246 -1.3862944 -0.8472979 -0.4054651  0.0000000
#>  [7]  0.4054651  0.8472979  1.3862944  2.1972246        Inf

# bound vector of unbounded values to [0, 1]
myvec <- rnorm(10)
expit(myvec)
#>  [1] 0.3788464 0.3648040 0.4510225 0.7326628 0.6156200 0.8123456 0.4121611
#>  [8] 0.1660213 0.9048911 0.1331326

# bound vector of unbounded values to [100, 200]
expit(myvec, lower_bound = 100, upper_bound = 200)
#>  [1] 137.8846 136.4804 145.1023 173.2663 161.5620 181.2346 141.2161 116.6021
#>  [9] 190.4891 113.3133