R: Log Minus Digamma Function

logmdigamma {statmod} | R Documentation

## Log Minus Digamma Function

### Description

The difference between the `log` and `digamma` functions.

### Usage

    logmdigamma(x)

### Arguments

`x` | numeric vector or array of positive values. Negative or zero values will return `NA`.

### Details

`digamma(x)` is asymptotically equivalent to `log(x)`. `logmdigamma(x)` computes `log(x) - digamma(x)` without subtractive cancellation for large `x`.

### Author(s)

Gordon Smyth

### References

Abramowitz, M., and Stegun, I. A. (1970). Handbook of mathematical functions. Dover, New York.

### See Also

`digamma`

### Examples

    log(10^15) - digamma(10^15) # returns 0
    logmdigamma(10^15) # returns value correct to 15 figures

[Package statmod version 1.4.32 Index]