# scipy.special.betaln#

scipy.special.betaln(a, b, out=None) = <ufunc 'betaln'>#

Natural logarithm of absolute value of beta function.

Computes `ln(abs(beta(a, b)))`.

Parameters:
a, barray_like

Positive, real-valued parameters

outndarray, optional

Optional output array for function values

Returns:
scalar or ndarray

Value of the betaln function

`gamma`

the gamma function

`betainc`

the regularized incomplete beta function

`beta`

the beta function

Examples

```>>> import numpy as np
>>> from scipy.special import betaln, beta
```

Verify that, for moderate values of `a` and `b`, `betaln(a, b)` is the same as `log(beta(a, b))`:

```>>> betaln(3, 4)
-4.0943445622221
```
```>>> np.log(beta(3, 4))
-4.0943445622221
```

In the following `beta(a, b)` underflows to 0, so we canâ€™t compute the logarithm of the actual value.

```>>> a = 400
>>> b = 900
>>> beta(a, b)
0.0
```

We can compute the logarithm of `beta(a, b)` by using `betaln`:

```>>> betaln(a, b)
-804.3069951764146
```