## The Exponential Distribution

Random: double gsl_ran_exponential (const gsl_rng * r, double mu)
  This function returns a random variate from the exponential distribution with mean mu. The distribution is,

      p(x) dx = {1 \over \mu} \exp(-x/\mu) dx

  for x >= 0.

Function: double gsl_ran_exponential_pdf (double x, double mu)
  This function computes the probability density p(x) at x for an exponential distribution with mean mu, using the formula given above.