# igamma

From distr v2.8.0
by Peter Ruckdeschel

##### Inverse of the digamma function

Function `igamma`

is a numerical inverse of `digamma`

.

- Keywords
- math

##### 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`

.

##### See Also

`digamma`

##### Examples

```
# NOT RUN {
igamma(digamma(c(1e-4,1,20,1e8)))
# }
```

*Documentation reproduced from package distr, version 2.8.0, License: LGPL-3*

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