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// Copyright 2019 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_custom_accumulators_advanced
#include <boost/format.hpp>
#include <boost/histogram.hpp>
#include <iostream>
#include <sstream>
int main() {
using namespace boost::histogram;
// Accumulator accepts two samples and an optional weight and computes the mean of each.
struct multi_mean {
accumulators::mean<> mx, my;
// called when no weight is passed
void operator()(double x, double y) {
mx(x);
my(y);
}
// called when a weight is passed
void operator()(weight_type<double> w, double x, double y) {
mx(w, x);
my(w, y);
}
};
// Note: The implementation can be made more efficient by sharing the sum of weights.
// Create a 1D histogram that uses the custom accumulator.
auto h = make_histogram_with(dense_storage<multi_mean>(), axis::integer<>(0, 2));
h(0, sample(1, 2)); // samples go to first cell
h(0, sample(3, 4)); // samples go to first cell
h(1, sample(5, 6), weight(2)); // samples go to second cell
h(1, sample(7, 8), weight(3)); // samples go to second cell
std::ostringstream os;
for (auto&& bin : indexed(h)) {
os << boost::format("index %i mean-x %.1f mean-y %.1f\n") % bin.index() %
bin->mx.value() % bin->my.value();
}
std::cout << os.str() << std::flush;
assert(os.str() == "index 0 mean-x 2.0 mean-y 3.0\n"
"index 1 mean-x 6.2 mean-y 7.2\n");
}
//]
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