ceph/src/boost/libs/histogram/examples/guide_fill_weighted_profile.cpp

   1 // Copyright 2019 Hans Dembinski
   2 //
   3 // Distributed under the Boost Software License, Version 1.0.
   4 // (See accompanying file LICENSE_1_0.txt
   5 // or copy at http://www.boost.org/LICENSE_1_0.txt)
   6
   7 //[ guide_fill_weighted_profile
   8
   9 #include <boost/format.hpp>
  10 #include <boost/histogram.hpp>
  11 #include <cassert>
  12 #include <iostream>
  13 #include <sstream>
  14
  15 int main() {
  16   using namespace boost::histogram;
  17   using namespace boost::histogram::literals; // _c suffix creates compile-time numbers
  18
  19   // make 2D weighted profile
  20   auto h = make_weighted_profile(axis::integer<>(0, 2), axis::integer<>(0, 2));
  21
  22   // The mean is computed from the values marked with the sample() helper function.
  23   // Weights can be passed as well. The `sample` and `weight` arguments can appear in any
  24   // order, but they must be the first or last arguments.
  25   h(0, 0, sample(1));            // sample goes to cell (0, 0); weight is 1
  26   h(0, 0, sample(2), weight(3)); // sample goes to cell (0, 0); weight is 3
  27   h(1, 0, sample(3));            // sample goes to cell (1, 0); weight is 1
  28   h(1, 0, sample(4));            // sample goes to cell (1, 0); weight is 1
  29   h(0, 1, sample(5));            // sample goes to cell (1, 0); weight is 1
  30   h(0, 1, sample(6));            // sample goes to cell (1, 0); weight is 1
  31   h(1, 1, weight(4), sample(7)); // sample goes to cell (1, 1); weight is 4
  32   h(weight(5), sample(8), 1, 1); // sample goes to cell (1, 1); weight is 5
  33
  34   std::ostringstream os;
  35   for (auto&& x : indexed(h)) {
  36     const auto i = x.index(0_c);
  37     const auto j = x.index(1_c);
  38     const auto m = x->value();    // weighted mean
  39     const auto v = x->variance(); // estimated variance of weighted mean
  40     os << boost::format("index %i,%i mean %.1f variance %.1f\n") % i % j % m % v;
  41   }
  42
  43   std::cout << os.str() << std::flush;
  44
  45   assert(os.str() == "index 0,0 mean 1.8 variance 0.5\n"
  46                      "index 1,0 mean 3.5 variance 0.5\n"
  47                      "index 0,1 mean 5.5 variance 0.5\n"
  48                      "index 1,1 mean 7.6 variance 0.5\n");
  49 }
  50
  51 //]