ceph/src/boost/libs/histogram/examples/guide_fill_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_profile
   8
   9 #include <boost/format.hpp>
  10 #include <boost/histogram.hpp>
  11 #include <cassert>
  12 #include <iostream>
  13 #include <sstream>
  14 #include <tuple>
  15
  16 int main() {
  17   using namespace boost::histogram;
  18
  19   // make a profile, it computes the mean of the samples in each histogram cell
  20   auto h = make_profile(axis::integer<>(0, 3));
  21
  22   // mean is computed from the values marked with the sample() helper function
  23   h(0, sample(1)); // sample goes to cell 0
  24   h(0, sample(2)); // sample goes to cell 0
  25   h(1, sample(3)); // sample goes to cell 1
  26   h(sample(4), 1); // sample goes to cell 1; sample can be first or last argument
  27
  28   // fills from tuples are also supported, 5 and 6 go to cell 2
  29   auto a = std::make_tuple(2, sample(5));
  30   auto b = std::make_tuple(sample(6), 2);
  31   h(a);
  32   h(b);
  33
  34   // builtin accumulators have methods to access their state
  35   std::ostringstream os;
  36   for (auto&& x : indexed(h)) {
  37     // use `.` to access methods of accessor, like `index()`
  38     // use `->` to access methods of accumulator
  39     const auto i = x.index();
  40     const auto n = x->count();     // how many samples are in this bin
  41     const auto vl = x->value();    // mean value
  42     const auto vr = x->variance(); // estimated variance of the mean value
  43     os << boost::format("index %i count %i value %.1f variance %.1f\n") % i % n % vl % vr;
  44   }
  45
  46   std::cout << os.str() << std::flush;
  47
  48   assert(os.str() == "index 0 count 2 value 1.5 variance 0.5\n"
  49                      "index 1 count 2 value 3.5 variance 0.5\n"
  50                      "index 2 count 2 value 5.5 variance 0.5\n");
  51 }
  52
  53 //]