Function quantile

src/openms/include/OpenMS/MATH/MISC/MathFunctions.h:363–378

       @brief Returns the value of the @p q th quantile (0-1) in a sorted non-empty vector @p x
    */
    template <typename T1> typename T1::value_type quantile(const T1 &x, double q)
    {
      if (x.empty()) throw Exception::InvalidParameter(__FILE__, __LINE__, OPENMS_PRETTY_FUNCTION,
                                                       "Quantile requested from empty container.");
      if (q < 0.0) q = 0.;
      if (q > 1.0) q = 1.;

      const auto n  = x.size();
      const auto id = std::max(0., n * q - 1); // -1 for c++ index starting at 0
      const auto lo = floor(id);
      const auto hi = ceil(id);
      const auto qs = x[lo];
      const auto h  = (id - lo);

      return (1.0 - h) * qs + h * x[hi];
    }

    // portable random shuffle
    class OPENMS_DLLAPI RandomShuffler