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- // Copyright 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_stdlib_algorithms
- #include <boost/histogram.hpp>
- #include <cassert>
- #include <algorithm> // fill, any_of, min_element, max_element
- #include <cmath> // sqrt
- #include <numeric> // partial_sum, inner_product
- int main() {
- using namespace boost::histogram;
- // make histogram that represents a probability density function (PDF)
- auto h1 = make_histogram(axis::regular<>(4, 1.0, 3.0));
- // make indexed range to skip underflow and overflow cells
- auto ind = indexed(h1);
- // use std::fill to set all counters to 0.25 (except under- and overflow counters)
- std::fill(ind.begin(), ind.end(), 0.25);
- // compute the cumulative density function (CDF), overriding cell values
- std::partial_sum(ind.begin(), ind.end(), ind.begin());
- assert(h1.at(-1) == 0.00);
- assert(h1.at(0) == 0.25);
- assert(h1.at(1) == 0.50);
- assert(h1.at(2) == 0.75);
- assert(h1.at(3) == 1.00);
- assert(h1.at(4) == 0.00);
- // use any_of to check if any cell values are smaller than 0.1,
- auto b = std::any_of(ind.begin(), ind.end(), [](const auto& x) { return x < 0.1; });
- assert(b == false); // under- and overflow cells are zero, but skipped
- // find minimum element
- auto min_it = std::min_element(ind.begin(), ind.end());
- assert(*min_it == 0.25); // under- and overflow cells are skipped
- // find maximum element
- auto max_it = std::max_element(ind.begin(), ind.end());
- assert(*max_it == 1.0);
- // make second PDF
- auto h2 = make_histogram(axis::regular<>(4, 1.0, 4.0));
- h2.at(0) = 0.1;
- h2.at(1) = 0.3;
- h2.at(2) = 0.2;
- h2.at(3) = 0.4;
- // computing cosine similiarity: cos(theta) = A dot B / sqrt((A dot A) * (B dot B))
- auto ind2 = indexed(h2);
- const auto aa = std::inner_product(ind.begin(), ind.end(), ind.begin(), 0.0);
- const auto bb = std::inner_product(ind2.begin(), ind2.end(), ind2.begin(), 0.0);
- const auto ab = std::inner_product(ind.begin(), ind.end(), ind2.begin(), 0.0);
- const auto cos_sim = ab / std::sqrt(aa * bb);
- assert(std::abs(cos_sim - 0.967) < 1e-2);
- }
- //]
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