R: Inverse of the digamma function

igamma {distr} | R Documentation

## Inverse of the digamma function

### Description

Function `igamma` is a numerical inverse of `digamma`.

### Usage

    igamma(v)

### Arguments

`v` | a numeric in the range [-100000,18]

### 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].

### Value

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

### Author(s)

Peter Ruckdeschel peter.ruckdeschel@uni-oldenburg.de

### See Also

`digamma`

### Examples

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

[Package distr version 2.8.0 Index]