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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_histogram_projection
- #include <boost/histogram.hpp>
- #include <cassert>
- #include <iostream>
- #include <sstream>
- int main() {
- using namespace boost::histogram;
- using namespace literals; // enables _c suffix
- // make a 2d histogram
- auto h = make_histogram(axis::regular<>(3, -1.0, 1.0), axis::integer<>(0, 2));
- h(-0.9, 0);
- h(0.9, 1);
- h(0.1, 0);
- auto hr0 = algorithm::project(h, 0_c); // keep only first axis
- auto hr1 = algorithm::project(h, 1_c); // keep only second axis
- // reduce does not remove counts; returned histograms are summed over
- // the removed axes, so h, hr0, and hr1 have same number of total counts;
- // we compute the sum of counts with the sum algorithm
- assert(algorithm::sum(h) == 3 && algorithm::sum(hr0) == 3 && algorithm::sum(hr1) == 3);
- std::ostringstream os1;
- for (auto&& x : indexed(h))
- os1 << "(" << x.index(0) << ", " << x.index(1) << "): " << *x << "\n";
- std::cout << os1.str() << std::flush;
- assert(os1.str() == "(0, 0): 1\n"
- "(1, 0): 1\n"
- "(2, 0): 0\n"
- "(0, 1): 0\n"
- "(1, 1): 0\n"
- "(2, 1): 1\n");
- std::ostringstream os2;
- for (auto&& x : indexed(hr0)) os2 << "(" << x.index(0) << ", -): " << *x << "\n";
- std::cout << os2.str() << std::flush;
- assert(os2.str() == "(0, -): 1\n"
- "(1, -): 1\n"
- "(2, -): 1\n");
- std::ostringstream os3;
- for (auto&& x : indexed(hr1)) os3 << "(- ," << x.index(0) << "): " << *x << "\n";
- std::cout << os3.str() << std::flush;
- assert(os3.str() == "(- ,0): 2\n"
- "(- ,1): 1\n");
- }
- //]
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