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62 lines
1.6 KiB
C++
62 lines
1.6 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_histogram_reduction
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#include <boost/histogram.hpp>
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#include <cassert>
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#include <sstream>
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namespace bh = boost::histogram;
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// example of a generic function for histograms, this one sums all entries
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template <typename... Ts>
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auto sum(const bh::histogram<Ts...>& h) {
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auto result = typename bh::histogram<Ts...>::value_type(0);
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for (auto x : h) result += x;
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return result;
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}
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int main() {
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using namespace bh::literals; // enables _c suffix
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// make a 2d histogram
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auto h = bh::make_histogram(bh::axis::regular<>(3, -1, 1), bh::axis::integer<>(0, 4));
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h(-0.9, 0);
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h(0.9, 3);
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h(0.1, 2);
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auto hr0 = bh::algorithm::project(h, 0_c); // keep only first axis
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auto hr1 = bh::algorithm::project(h, 1_c); // keep only second axis
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/*
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reduce does not remove counts; returned histograms are summed over
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the removed axes, so h, hr0, and hr1 have same number of total counts
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*/
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assert(sum(h) == 3 && sum(hr0) == 3 && sum(hr1) == 3);
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std::ostringstream os1;
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for (auto yi : h.axis(1_c)) {
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for (auto xi : h.axis(0_c)) { os1 << h.at(xi, yi) << " "; }
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os1 << "\n";
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}
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assert(os1.str() == "1 0 0 \n"
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"0 0 0 \n"
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"0 1 0 \n"
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"0 0 1 \n");
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std::ostringstream os2;
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for (auto xi : hr0.axis()) os2 << hr0.at(xi) << " ";
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assert(os2.str() == "1 1 1 ");
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std::ostringstream os3;
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for (auto yi : hr1.axis()) os3 << hr1.at(yi) << " ";
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assert(os3.str() == "1 0 1 1 ");
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}
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//]
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