.. _program_listing_file_include_rttest_math_utils.hpp:

Program Listing for File math_utils.hpp
=======================================

|exhale_lsh| :ref:`Return to documentation for file <file_include_rttest_math_utils.hpp>` (``include/rttest/math_utils.hpp``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   // Copyright 2020 Open Source Robotics Foundation, Inc.
   //
   // Licensed under the Apache License, Version 2.0 (the "License");
   // you may not use this file except in compliance with the License.
   // You may obtain a copy of the License at
   //
   //     http://www.apache.org/licenses/LICENSE-2.0
   //
   // Unless required by applicable law or agreed to in writing, software
   // distributed under the License is distributed on an "AS IS" BASIS,
   // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   // See the License for the specific language governing permissions and
   // limitations under the License.
   
   #ifndef RTTEST__MATH_UTILS_HPP_
   #define RTTEST__MATH_UTILS_HPP_
   
   #include <algorithm>
   #include <cmath>
   #include <numeric>
   #include <vector>
   
   template<typename container>
   double calculate_stddev(const container & vec)
   {
     double n = vec.size();
     double mean = std::accumulate(
       vec.begin(),
       vec.end(), 0.0) / n;
   
     std::vector<double> diff(n);
     std::transform(
       vec.begin(), vec.end(), diff.begin(),
       [mean](auto x) -> double {return x - mean;});
   
     // first divide by sqrt(n)
     std::vector<double> div(n);
     std::transform(
       diff.begin(), diff.end(), div.begin(),
       [n](auto x) -> double {return x / std::sqrt(n);});
   
     // inner_product
     double sq_sum = std::inner_product(
       div.begin(), div.end(), div.begin(), 0.0);
   
     return std::sqrt(sq_sum);
   }
   
   #endif  // RTTEST__MATH_UTILS_HPP_