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63 lines
2.1 KiB
C++
63 lines
2.1 KiB
C++
//[ guide_access_bin_counts
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#include <boost/histogram.hpp>
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#include <iostream>
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#include <numeric>
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namespace bh = 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 = bh::make_static_histogram(bh::axis::regular<>(2, -1, 1),
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bh::axis::regular<>(2, 2, 4));
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h(bh::weight(1), -0.5, 2.5); // bin index 0, 0
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h(bh::weight(2), -0.5, 3.5); // bin index 0, 1
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h(bh::weight(3), 0.5, 2.5); // bin index 1, 0
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h(bh::weight(4), 0.5, 3.5); // bin index 1, 1
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// access count value, number of indices must match number of axes
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std::cout << h.at(0, 0).value() << " " << h.at(0, 1).value() << " "
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<< h.at(1, 0).value() << " " << h.at(1, 1).value() << std::endl;
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// prints: 1 2 3 4
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// access count variance, number of indices must match number of axes
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std::cout << h.at(0, 0).variance() << " " << h.at(0, 1).variance() << " "
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<< h.at(1, 0).variance() << " " << h.at(1, 1).variance()
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<< std::endl;
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// prints: 1 4 9 16
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// this is more efficient when you want to query value and variance
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auto c11 = h.at(1, 1);
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std::cout << c11.value() << " " << c11.variance() << std::endl;
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// prints: 4 16
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// histogram also supports access via container; using a container of
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// wrong size trips an assertion in debug mode
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auto idx = {0, 1};
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std::cout << h.at(idx).value() << std::endl;
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// prints: 2
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// histogram also provides bin iterators
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auto sum = std::accumulate(h.begin(), h.end(),
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typename decltype(h)::element_type(0));
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std::cout << sum.value() << " " << sum.variance() << std::endl;
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// prints: 10 30
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// bin iterators are fancy iterators with extra methods
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for (auto it = h.begin(), end = h.end(); it != end; ++it) {
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const auto x = *it;
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std::cout << it.idx(0) << " " << it.idx(1) << ": "
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<< x.value() << " " << x.variance() << std::endl;
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}
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// prints: (iteration order is an implementation detail, don't rely on it)
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// 0 0: 1 1
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// 1 0: 3 9
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// ...
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// 2 -1: 0 0
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// -1 -1: 0 0
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}
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//]
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