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57 lines
1.5 KiB
C++
57 lines
1.5 KiB
C++
//[ guide_histogram_operators
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#include <boost/histogram.hpp>
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#include <cassert>
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#include <vector>
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namespace bh = boost::histogram;
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int main() {
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// make two histograms
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auto h1 = bh::make_histogram(bh::axis::regular<>(2, -1, 1));
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auto h2 = bh::make_histogram(bh::axis::regular<>(2, -1, 1));
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h1(-0.5); // counts are: 1 0
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h2(0.5); // counts are: 0 1
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// add them
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auto h3 = h1;
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h3 += h2; // counts are: 1 1
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// adding multiple histograms at once is efficient and does not create
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// superfluous temporaries since operator+ functions are overloaded to
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// accept and return rvalue references where possible
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auto h4 = h1 + h2 + h3; // counts are: 2 2
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assert(h4.at(0) == 2 && h4.at(1) == 2);
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// multiply by number
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h4 *= 2; // counts are: 4 4
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// divide by number
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auto h5 = h4 / 4; // counts are: 1 1
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assert(h5.at(0) == 1 && h5.at(1) == 1);
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assert(h4 != h5 && h4 == 4 * h5);
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// note special effect of multiplication on weight_counter variance
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auto h = bh::make_histogram_with(std::vector<bh::weight_counter<double>>(),
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bh::axis::regular<>(2, -1, 1));
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h(-0.5);
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// counts are: 1 0
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assert(h.at(0).value() == 1 && h.at(1).value() == 0);
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auto h_sum = h + h;
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auto h_mul = 2 * h;
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// equality operator checks variances, so following statement is false
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assert(h_sum != h_mul);
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// variance is different when histograms are scaled
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assert(h_sum.at(0).value() == 2 && h_mul.at(0).value() == 2);
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assert(h_sum.at(0).variance() == 2 && h_mul.at(0).variance() == 4);
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}
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//]
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