Function beta

beta(a: number, b: number): number
Beta function B(a, b). Equivalent to R's beta(). Takes single numbers.
Parameters
- a: number
  First argument.
- b: number
  Second argument.
Returns number
B(a, b).
Example
```
beta(2, 3);  // 0.08333333333333333
```
- Defined in special/beta.ts:38