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// Copyright 2015-2018 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)
// clang-format off
//[ getting_started_listing_01
#include <algorithm> // std::for_each
#include <boost/format.hpp> // only needed for printing
#include <boost/histogram.hpp> // make_histogram, regular, weight, indexed
#include <cassert> // assert (used to test this example for correctness)
#include <functional> // std::ref
#include <iostream> // std::cout, std::flush
#include <sstream> // std::ostringstream
int main() {
using namespace boost::histogram; // strip the boost::histogram prefix
/*
Create a 1d-histogram with a regular axis that has 6 equidistant bins on
the real line from -1.0 to 2.0, and label it as "x". A family of overloaded
factory functions called `make_histogram` makes creating histograms easy.
A regular axis is a sequence of semi-open bins. Extra under- and overflow
bins extend the axis by default (this can be turned off).
index : -1 | 0 | 1 | 2 | 3 | 4 | 5 | 6
bin edges: -inf -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 inf
*/
auto h = make_histogram(axis::regular<>(6, -1.0, 2.0, "x"));
/*
Let's fill a histogram with data, typically this happens in a loop.
STL algorithms are supported. std::for_each is very convenient to fill a
histogram from an iterator range. Use std::ref in the call, if you don't
want std::for_each to make a copy of your histogram.
*/
auto data = {-0.5, 1.1, 0.3, 1.7};
std::for_each(data.begin(), data.end(), std::ref(h));
// let's fill some more values manually
h(-1.5); // is placed in underflow bin -1
h(-1.0); // is placed in bin 0, bin interval is semi-open
h(2.0); // is placed in overflow bin 6, bin interval is semi-open
h(20.0); // is placed in overflow bin 6
/*
This does a weighted fill using the `weight` function as an additional
argument. It may appear at the beginning or end of the argument list. C++
doesn't have keyword arguments like Python, this is the next-best thing.
*/
h(0.1, weight(1.0));
/*
Iterate over bins with the `indexed` range generator, which provides a
special accessor object, that can be used to obtain the current bin index,
and the current bin value by dereferncing (it acts like a pointer to the
value). Using `indexed` is convenient and gives you better performance than
looping over the histogram cells with hand-written for loops. By default,
under- and overflow bins are skipped. Passing `coverage::all` as the
optional second argument iterates over all bins.
- Access the value with the dereference operator.
- Access the current index with `index(d)` method of the accessor.
- Access the corresponding bin interval view with `bin(d)`.
The return type of `bin(d)` depends on the axis type (see the axis reference
for details). It usually is a class that represents a semi-open interval.
Edges can be accessed with methods `lower()` and `upper()`.
*/
std::ostringstream os;
for (auto&& x : indexed(h, coverage::all)) {
os << boost::format("bin %2i [%4.1f, %4.1f): %i\n")
% x.index() % x.bin().lower() % x.bin().upper() % *x;
}
std::cout << os.str() << std::flush;
assert(os.str() == "bin -1 [-inf, -1.0): 1\n"
"bin 0 [-1.0, -0.5): 1\n"
"bin 1 [-0.5, -0.0): 1\n"
"bin 2 [-0.0, 0.5): 2\n"
"bin 3 [ 0.5, 1.0): 0\n"
"bin 4 [ 1.0, 1.5): 1\n"
"bin 5 [ 1.5, 2.0): 1\n"
"bin 6 [ 2.0, inf): 2\n");
}
//]
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