code: public function rho($float_min, $float_max)
      {
          self::checkOrder($float_min, $float_max);
  
          if ($float_min < 0 || $float_max < 0) {
              throw new \InvalidArgumentException('Rho value must be a positive number!');
          }
  
          if ($this->r || $this->i) {
              throw new \RuntimeException('You cannot set rho value, because algebraic form is in use.');
          }
  
          $this->rho = new \stdClass();
          $this->rho->min = $float_min;
          $this->rho->max = $float_max;
  
          return $this;
      }
docs: Sets min and max value for random rho
  
  @throw \InvalidArgumentException If rho is not positive number.
  @throw \RuntimeException If this is called into algebraic context.
  @param  float         $float_min
  @param  float         $float_max
  @access public
  @return RandomComplex