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1 | // Copyright 2019 Hans Dembinski |
2 | // | |
3 | // Distributed under the Boost Software License, Version 1.0. | |
4 | // (See accompanying file LICENSE_1_0.txt | |
5 | // or copy at http://www.boost.org/LICENSE_1_0.txt) | |
6 | ||
f67539c2 | 7 | //[ guide_custom_accumulators_advanced |
92f5a8d4 TL |
8 | |
9 | #include <boost/format.hpp> | |
10 | #include <boost/histogram.hpp> | |
11 | #include <iostream> | |
12 | #include <sstream> | |
13 | ||
14 | int main() { | |
15 | using namespace boost::histogram; | |
16 | ||
17 | // Accumulator accepts two samples and an optional weight and computes the mean of each. | |
18 | struct multi_mean { | |
19 | accumulators::mean<> mx, my; | |
20 | ||
21 | // called when no weight is passed | |
22 | void operator()(double x, double y) { | |
23 | mx(x); | |
24 | my(y); | |
25 | } | |
26 | ||
27 | // called when a weight is passed | |
28 | void operator()(weight_type<double> w, double x, double y) { | |
29 | mx(w, x); | |
30 | my(w, y); | |
31 | } | |
32 | }; | |
33 | // Note: The implementation can be made more efficient by sharing the sum of weights. | |
34 | ||
35 | // Create a 1D histogram that uses the custom accumulator. | |
36 | auto h = make_histogram_with(dense_storage<multi_mean>(), axis::integer<>(0, 2)); | |
37 | h(0, sample(1, 2)); // samples go to first cell | |
38 | h(0, sample(3, 4)); // samples go to first cell | |
39 | h(1, sample(5, 6), weight(2)); // samples go to second cell | |
40 | h(1, sample(7, 8), weight(3)); // samples go to second cell | |
41 | ||
42 | std::ostringstream os; | |
43 | for (auto&& bin : indexed(h)) { | |
44 | os << boost::format("index %i mean-x %.1f mean-y %.1f\n") % bin.index() % | |
45 | bin->mx.value() % bin->my.value(); | |
46 | } | |
47 | std::cout << os.str() << std::flush; | |
48 | assert(os.str() == "index 0 mean-x 2.0 mean-y 3.0\n" | |
49 | "index 1 mean-x 6.2 mean-y 7.2\n"); | |
50 | } | |
51 | ||
52 | //] |