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- // Copyright 2015-2018 Hans Dembinski
- //
- // Distributed under the Boost Software License, Version 1.0.
- // (See accompanying file LICENSE_1_0.txt
- // or copy at http://www.boost.org/LICENSE_1_0.txt)
- //[ guide_indexed_access
- #include <boost/format.hpp>
- #include <boost/histogram.hpp>
- #include <cassert>
- #include <iostream>
- #include <numeric> // for std::accumulate
- #include <sstream>
- using namespace boost::histogram;
- int main() {
- // make histogram with 2 x 2 = 4 bins (not counting under-/overflow bins)
- auto h = make_histogram(axis::regular<>(2, -1.0, 1.0), axis::regular<>(2, 2.0, 4.0));
- h(weight(1), -0.5, 2.5); // bin index 0, 0
- h(weight(2), -0.5, 3.5); // bin index 0, 1
- h(weight(3), 0.5, 2.5); // bin index 1, 0
- h(weight(4), 0.5, 3.5); // bin index 1, 1
- // use the `indexed` range adaptor to iterate over all bins;
- // it is not only more convenient but also faster than a hand-crafted loop!
- std::ostringstream os;
- for (auto&& x : indexed(h)) {
- // x is a special accessor object
- const auto i = x.index(0); // current index along first axis
- const auto j = x.index(1); // current index along second axis
- const auto b0 = x.bin(0); // current bin interval along first axis
- const auto b1 = x.bin(1); // current bin interval along second axis
- const auto v = *x; // "dereference" to get the bin value
- os << boost::format("%i %i [%2i, %i) [%2i, %i): %i\n") % i % j % b0.lower() %
- b0.upper() % b1.lower() % b1.upper() % v;
- }
- std::cout << os.str() << std::flush;
- assert(os.str() == "0 0 [-1, 0) [ 2, 3): 1\n"
- "1 0 [ 0, 1) [ 2, 3): 3\n"
- "0 1 [-1, 0) [ 3, 4): 2\n"
- "1 1 [ 0, 1) [ 3, 4): 4\n");
- // `indexed` skips underflow and overflow bins by default, but can be called
- // with the second argument `coverage::all` to walk over all bins
- std::ostringstream os2;
- for (auto&& x : indexed(h, coverage::all)) {
- os2 << boost::format("%2i %2i: %i\n") % x.index(0) % x.index(1) % *x;
- }
- std::cout << os2.str() << std::flush;
- assert(os2.str() == "-1 -1: 0\n"
- " 0 -1: 0\n"
- " 1 -1: 0\n"
- " 2 -1: 0\n"
- "-1 0: 0\n"
- " 0 0: 1\n"
- " 1 0: 3\n"
- " 2 0: 0\n"
- "-1 1: 0\n"
- " 0 1: 2\n"
- " 1 1: 4\n"
- " 2 1: 0\n"
- "-1 2: 0\n"
- " 0 2: 0\n"
- " 1 2: 0\n"
- " 2 2: 0\n");
- }
- //]
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