Returns the probability density at x for this Gumbel distribution.
The density is computed using the standardized variable z = (x - mu) / beta as exp(-(z + exp(-z))) / beta. The left tail decays doubly-exponentially (much faster than the right tail), so density values near the left extreme may underflow to zero.
Return
the probability density at x. Always non-negative.
Parameters
x
the point at which to evaluate the density.