RhodeCode

    /// Lognormal distribution

    /// Lognormal distribution. The parameters are the mean and the standard

    /// deviation of <tt>exp(X)</tt>.

    ///

    double lognormal(double n_mean,double n_std_dev)

    {

      return std::exp(gauss(n_mean,n_std_dev));

    }

    /// Lognormal distribution

    /// Lognormal distribution. The parameter is an <tt>std::pair</tt> of

    /// the mean and the standard deviation of <tt>exp(X)</tt>.

    ///

    double lognormal(const std::pair<double,double> &params)

    {

      return std::exp(gauss(params.first,params.second));

    }

    /// Compute the lognormal parameters from mean and standard deviation

    /// This function computes the lognormal parameters from mean and

    /// standard deviation. The return value can direcly be passed to

    /// lognormal().

    std::pair<double,double> lognormalParamsFromMD(double mean,

						   double std_dev)

    {

      double fr=std_dev/mean;

      fr*=fr;

      double lg=std::log(1+fr);

      return std::pair<double,double>(std::log(mean)-lg/2.0,std::sqrt(lg));

    }

    /// Lognormal distribution with given mean and standard deviation

    /// Lognormal distribution with given mean and standard deviation.

    ///

    double lognormalMD(double mean,double std_dev)

    {

      return lognormal(lognormalParamsFromMD(mean,std_dev));

    }