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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_custom_accumulators_1
- #include <boost/format.hpp>
- #include <boost/histogram.hpp>
- #include <cassert>
- #include <iostream>
- #include <sstream>
- int main() {
- using namespace boost::histogram;
- using mean = accumulators::mean<>;
- // Create a 1D-profile, which computes the mean of samples in each bin.
- auto h = make_histogram_with(dense_storage<mean>(), axis::integer<>(0, 2));
- // The factory function `make_profile` is provided as a shorthand for this, so this is
- // equivalent to the previous line: auto h = make_profile(axis::integer<>(0, 2));
- // An argument marked as `sample` is passed to the accumulator.
- h(0, sample(1)); // sample goes to first cell
- h(0, sample(2)); // sample goes to first cell
- h(1, sample(3)); // sample goes to second cell
- h(1, sample(4)); // sample goes to second cell
- std::ostringstream os;
- for (auto&& x : indexed(h)) {
- // Accumulators usually have methods to access their state. Use the arrow
- // operator to access them. Here, `count()` gives the number of samples,
- // `value()` the mean, and `variance()` the variance estimate of the mean.
- os << boost::format("index %i count %i mean %.1f variance %.1f\n") % x.index() %
- x->count() % x->value() % x->variance();
- }
- std::cout << os.str() << std::flush;
- assert(os.str() == "index 0 count 2 mean 1.5 variance 0.5\n"
- "index 1 count 2 mean 3.5 variance 0.5\n");
- }
- //]
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