### 20.22 The Logistic Distribution

Function: double gsl_ran_logistic (const gsl_rng * r, double a)

  This function returns a random variate from the logistic distribution. The distribution function is,

      p(x) dx = { \exp(-x/a) \over a (1 + \exp(-x/a))^2 } dx

  for -\infty < x < +\infty.

Function: double gsl_ran_logistic_pdf (double x, double a)

  This function computes the probability density p(x) at x for a logistic distribution with scale parameter a, using the formula given above.

Function: double gsl_cdf_logistic_P (double x, double a)
Function: double gsl_cdf_logistic_Q (double x, double a)
Function: double gsl_cdf_logistic_Pinv (double P, double a)
Function: double gsl_cdf_logistic_Qinv (double Q, double a)

  These functions compute the cumulative distribution functions P(x), Q(x) and their inverses for the logistic distribution with scale parameter a.