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68 lines
2.2 KiB
C++
68 lines
2.2 KiB
C++
// Copyright 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_stl_algorithms
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#include <boost/histogram.hpp>
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#include <cassert>
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#include <algorithm> // fill, any_of, min_element, max_element
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#include <cmath> // sqrt
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#include <numeric> // partial_sum, inner_product
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namespace bh = boost::histogram;
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int main() {
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// make histogram and set all cells to 0.25, simulating a perfectly uniform PDF,
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// this includes underflow and overflow cells
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auto a = bh::make_histogram(bh::axis::regular<>(4, 1.0, 3.0));
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std::fill(a.begin(), a.end(), 0.25); // set all counters to 0.25, including *flow cells
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// reset *flow cells to zero
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a.at(-1) = a.at(4) = 0;
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// compute CDF, overriding cell values
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std::partial_sum(a.begin(), a.end(), a.begin());
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assert(a.at(-1) == 0.0);
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assert(a.at(0) == 0.25);
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assert(a.at(1) == 0.50);
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assert(a.at(2) == 0.75);
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assert(a.at(3) == 1.00);
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assert(a.at(4) == 1.00);
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// use any_of to check if any cell values are smaller than 0.1,
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// and use indexed() to skip underflow and overflow cells
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auto a_ind = indexed(a);
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const auto any_small =
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std::any_of(a_ind.begin(), a_ind.end(), [](const auto& x) { return *x < 0.1; });
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assert(any_small == false); // underflow and overflow are zero, but skipped
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// find maximum element
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const auto max_it = std::max_element(a.begin(), a.end());
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assert(max_it == a.end() - 2);
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// find minimum element
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const auto min_it = std::min_element(a.begin(), a.end());
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assert(min_it == a.begin());
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// make second PDF
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auto b = bh::make_histogram(bh::axis::regular<>(4, 1.0, 4.0));
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b.at(0) = 0.1;
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b.at(1) = 0.3;
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b.at(2) = 0.2;
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b.at(3) = 0.4;
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// computing cosine similiarity: cos(theta) = A dot B / sqrt((A dot A) * (B dot B))
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const auto aa = std::inner_product(a.begin(), a.end(), a.begin(), 0.0);
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const auto bb = std::inner_product(b.begin(), b.end(), b.begin(), 0.0);
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const auto ab = std::inner_product(a.begin(), a.end(), b.begin(), 0.0);
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const auto cos_sim = ab / std::sqrt(aa * bb);
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assert(std::abs(cos_sim - 0.78) < 1e-2);
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}
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//]
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