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92 lines
3.0 KiB
C++
92 lines
3.0 KiB
C++
// Copyright 2015-2018 Hans Dembinski
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt
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// or copy at http://www.boost.org/LICENSE_1_0.txt)
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//[ guide_access_bin_counts
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#include <boost/format.hpp>
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#include <boost/histogram.hpp>
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#include <cassert>
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#include <numeric> // for std::accumulate
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using namespace boost::histogram;
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int main() {
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// make histogram with 2 x 2 = 4 bins (not counting under-/overflow bins)
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auto h = make_histogram(axis::regular<>(2, -1.0, 1.0), axis::regular<>(2, 2.0, 4.0));
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h(weight(1), -0.5, 2.5); // bin index 0, 0
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h(weight(2), -0.5, 3.5); // bin index 0, 1
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h(weight(3), 0.5, 2.5); // bin index 1, 0
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h(weight(4), 0.5, 3.5); // bin index 1, 1
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// histogram has bin iterators which iterate over all bin values including
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// underflow/overflow; it works with STL algorithms
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auto sum = std::accumulate(h.begin(), h.end(), 0.0);
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assert(sum == 10);
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// access individual bins with `at`
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assert(h.at(0, 0) == 1);
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assert(h.at(0, 1) == 2);
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assert(h.at(1, 0) == 3);
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assert(h.at(1, 1) == 4);
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// index tuples are also supported
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auto idx = std::make_tuple(0, 1);
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assert(h.at(idx) == 2);
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// use the `indexed` range adaptor to iterate over all bins;
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// it is not only more convenient but also faster than a hand-crafted loop!
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std::ostringstream os;
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for (auto x : indexed(h)) {
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// x is a special accessor object
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const auto i = x.index(0); // current index along first axis
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const auto j = x.index(1); // current index along second axis
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const auto b0 = x.bin(0); // current bin interval along first axis
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const auto b1 = x.bin(1); // current bin interval along second axis
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const auto v = *x; // "dereference" to get the bin value
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os << boost::format("%i %i [%2i, %i) [%2i, %i): %i\n") % i % j % b0.lower() %
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b0.upper() % b1.lower() % b1.upper() % v;
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}
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std::cout << os.str() << std::flush;
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assert(os.str() == "0 0 [-1, 0) [ 2, 3): 1\n"
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"1 0 [ 0, 1) [ 2, 3): 3\n"
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"0 1 [-1, 0) [ 3, 4): 2\n"
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"1 1 [ 0, 1) [ 3, 4): 4\n");
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// `indexed` skips underflow and overflow bins by default, but can be called with the
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// second argument `coverage::all` to walk over all bins
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std::ostringstream os2;
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for (auto x : indexed(h, coverage::all)) {
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os2 << boost::format("%2i %2i: %i\n") % x.index(0) % x.index(1) % *x;
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}
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std::cout << os2.str() << std::flush;
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assert(os2.str() == "-1 -1: 0\n"
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" 0 -1: 0\n"
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" 1 -1: 0\n"
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" 2 -1: 0\n"
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"-1 0: 0\n"
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" 0 0: 1\n"
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" 1 0: 3\n"
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" 2 0: 0\n"
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"-1 1: 0\n"
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" 0 1: 2\n"
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" 1 1: 4\n"
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" 2 1: 0\n"
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"-1 2: 0\n"
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" 0 2: 0\n"
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" 1 2: 0\n"
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" 2 2: 0\n");
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}
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//]
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