Computes the logit transformation logit \(=\log [p/(1-p)]\)
for the proportion \(p\).

If \(p=0\) or \(1\), then the logit
is undefined. `logit`

can remap the proportions to the interval
`(adjust, 1 - adjust)`

prior to the transformation. If it adjusts the data
automatically, `logit`

will print a warning message.