Metalog3PRV
A three-term metalog random variable.
The third coefficient controls skewness, positive skewing right and negative skewing left.
Because the metalog quantile function is closed form, each variate costs one evaluation of it, with no root finding and no rejection. Which member of the family this represents follows from which bounds are finite rather than from a separate setting.
The coefficients are validated once here and are immutable thereafter, so generation performs no feasibility checking at all. That is safe because the parameters of a random variable are never mutated in place: a parameter change in a running model is applied by constructing a fresh instance, which revalidates. It is also necessary, since an invalid coefficient vector does not fail during generation but instead silently produces values that are not a sample from any distribution.
Parameters
the location, which is the median in fitting space
the scale, which must be strictly positive
the skewness coefficient
the lower bound, or negative infinity when unbounded below
the upper bound, or positive infinity when unbounded above
the random number stream number, defaults to 0, which means the next stream
the provider of random number streams
an optional name