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86 lines
3.1 KiB
C++
86 lines
3.1 KiB
C++
// Copyright 2015-2018 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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//[ getting_started_listing_01
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#include <algorithm>
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#include <boost/histogram.hpp>
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#include <cassert>
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#include <functional>
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#include <sstream>
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int main() {
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using namespace boost::histogram;
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/*
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Create a 1d-histogram with an axis that has 6 equidistant
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bins on the real line from -1.0 to 2.0, and label it as "x".
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*/
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auto h = make_histogram(axis::regular<>(6, -1.0, 2.0, "x"));
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/*
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Fill histogram with data, typically this happens in a loop.
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STL algorithms are supported. std::for_each is very convenient
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to fill a histogram from an iterator range. Make sure to
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use std::ref in the call, otherwise it will fill a copy of
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the histogram and return it, which is less efficient.
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*/
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auto data = {-0.5, 1.1, 0.3, 1.7};
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std::for_each(data.begin(), data.end(), std::ref(h));
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/*
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A regular axis is a sequence of semi-open bins. Extra under- and
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overflow bins extend the axis in the default configuration.
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index : -1 0 1 2 3 4 5 6
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bin edges: -inf -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 inf
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*/
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h(-1.5); // put in underflow bin -1
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h(-1.0); // put in bin 0, bin interval is semi-open
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h(2.0); // put in overflow bin 6, bin interval is semi-open
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h(20.0); // put in overflow bin 6
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/*
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Do a weighted fill using the `weight` function as an additional
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argument. It may appear at the beginning or end of the argument list.
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*/
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h(0.1, weight(1.0));
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/*
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Iterate over bins with a fancy histogram iterator
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- order in which bins are iterated over is an implementation detail
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- iterator dereferences to histogram::const_reference, which is defined by
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its storage class; for the default storage it is actually a plain double
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- idx(N) method returns the index of the N-th axis
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- bin(N_c) method returns current bin of N-th axis; the suffx _c turns
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the argument into a compile-time number, which is needed to return
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a different `bin_type`s for each axis
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- `bin_type` usually is a semi-open interval representing the bin, whose
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edges can be accessed with methods `lower()` and `upper()`, but the
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implementation depends on the axis, please look it up in the reference
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*/
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std::ostringstream os;
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os.setf(std::ios_base::fixed);
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for (auto x : indexed(h)) {
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os << "bin " << std::setw(2) << x[0] << " [" << std::setprecision(1) << std::setw(4)
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<< x.bin(0).lower() << ", " << std::setw(4) << x.bin(0).upper()
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<< "): " << std::fixed << x.value << "\n";
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}
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std::cout << os.str() << std::endl;
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assert(os.str() == "bin 0 [-1.0, -0.5): 1.0\n"
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"bin 1 [-0.5, -0.0): 1.0\n"
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"bin 2 [-0.0, 0.5): 2.0\n"
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"bin 3 [ 0.5, 1.0): 0.0\n"
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"bin 4 [ 1.0, 1.5): 1.0\n"
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"bin 5 [ 1.5, 2.0): 1.0\n"
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"bin 6 [ 2.0, inf): 2.0\n"
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"bin -1 [-inf, -1.0): 1.0\n");
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// note how under- and overflow bins appear at the end
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}
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//]
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