14f36ea932
* new accmulator examples for user guide * new weighted profile example * minor corrections to other examples
44 lines
1.6 KiB
C++
44 lines
1.6 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_custom_accumulators_1
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#include <boost/format.hpp>
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#include <boost/histogram.hpp>
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#include <cassert>
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#include <iostream>
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#include <sstream>
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int main() {
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using namespace boost::histogram;
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using mean = accumulators::mean<>;
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// Create a 1D-profile, which computes the mean of samples in each bin.
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auto h = make_histogram_with(dense_storage<mean>(), axis::integer<>(0, 2));
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// The factory function `make_profile` is provided as a shorthand for this, so this is
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// equivalent to the previous line: auto h = make_profile(axis::integer<>(0, 2));
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// An argument marked as `sample` is passed to the accumulator.
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h(0, sample(1)); // sample goes to first cell
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h(0, sample(2)); // sample goes to first cell
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h(1, sample(3)); // sample goes to second cell
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h(1, sample(4)); // sample goes to second cell
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std::ostringstream os;
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for (auto&& x : indexed(h)) {
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// Accumulators usually have methods to access their state. Use the arrow
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// operator to access them. Here, `count()` gives the number of samples,
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// `value()` the mean, and `variance()` the variance estimate of the mean.
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os << boost::format("index %i count %i mean %.1f variance %.1f\n") % x.index() %
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x->count() % x->value() % x->variance();
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}
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std::cout << os.str() << std::flush;
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assert(os.str() == "index 0 count 2 mean 1.5 variance 0.5\n"
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"index 1 count 2 mean 3.5 variance 0.5\n");
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}
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//]
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