Convenience functions for logit/sigmoid mappings

Returns functions that map \(x \mapsto \log(\frac{ax+b}{1-ax+b})\) and \(x \mapsto \frac{\exp(x)(1+b)-b}{a(1+\exp(x))}\). (These are inverses.)

logit_pad(a = 1, b = 0.01)

sigmd_pad(a = 1, b = 0.011)