distr (version 2.8.0)

igamma: Inverse of the digamma function

Description

Function igamma is a numerical inverse of digamma.

Usage

igamma(v)

Value

igamma(x) is a value u such that digamma(u is approximately x.

Arguments

v

a numeric in the range [-100000,18]

Author

Peter Ruckdeschel

Details

igamma is vectorized; it is won by spline inversion of a grid; it works well for range [digamma(1e-5);digamma(1e8)] or [-100000,18].

See Also

digamma

Examples

igamma(digamma(c(1e-4,1,20,1e8)))