1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Function template sum</title> 5<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../index.html" title="Chapter 1. Boost.Histogram"> 8<link rel="up" href="../../../histogram/reference.html#header.boost.histogram.algorithm.sum_hpp" title="Header <boost/histogram/algorithm/sum.hpp>"> 9<link rel="prev" href="slice_an_idm45503931040864.html" title="Function slice_and_rebin"> 10<link rel="next" href="../axis/boolean.html" title="Class template boolean"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="slice_an_idm45503931040864.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../histogram/reference.html#header.boost.histogram.algorithm.sum_hpp"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../axis/boolean.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="refentry"> 26<a name="boost.histogram.algorithm.sum"></a><div class="titlepage"></div> 27<div class="refnamediv"> 28<h2><span class="refentrytitle">Function template sum</span></h2> 29<p>boost::histogram::algorithm::sum — Compute the sum over all histogram cells (underflow/overflow included by default). </p> 30</div> 31<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 32<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../../../histogram/reference.html#header.boost.histogram.algorithm.sum_hpp" title="Header <boost/histogram/algorithm/sum.hpp>">boost/histogram/algorithm/sum.hpp</a>> 33 34</span> 35<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> A<span class="special">,</span> <span class="keyword">typename</span> S<span class="special">></span> 36 <span class="keyword">auto</span> <span class="identifier">sum</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="../histogram.html" title="Class template histogram">histogram</a><span class="special"><</span> <span class="identifier">A</span><span class="special">,</span> <span class="identifier">S</span> <span class="special">></span> <span class="special">&</span> hist<span class="special">,</span> <span class="keyword">const</span> <span class="identifier">coverage</span> cov <span class="special">=</span> <span class="identifier">coverage</span><span class="special">::</span><span class="identifier">all</span><span class="special">)</span><span class="special">;</span></pre></div> 37<div class="refsect1"> 38<a name="idm45113194757408"></a><h2>Description</h2> 39<p>The implementation favors accuracy and protection against overflow over speed. If the value type of the histogram is an integral or floating point type, accumulators::sum<double> is used to compute the sum, else the original value type is used. Compilation fails, if the value type does not support operator+=. The return type is double if the value type of the histogram is integral or floating point, and the original value type otherwise.</p> 40<p>If you need a different trade-off, you can write your own loop or use <code class="computeroutput">std::accumulate</code>:</p> 41<pre class="programlisting"><span class="comment">// iterate over all bins</span> 42<span class="keyword">auto</span> <span class="identifier">sum_all</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">accumulate</span><span class="special">(</span><span class="identifier">hist</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(</span><span class="special">)</span><span class="special">,</span> <span class="identifier">hist</span><span class="special">.</span><span class="identifier">end</span><span class="special">(</span><span class="special">)</span><span class="special">,</span> <span class="number">0</span><span class="special">.</span><span class="number">0</span><span class="special">)</span><span class="special">;</span> 43 44<span class="comment">// skip underflow/overflow bins</span> 45<span class="keyword">double</span> <span class="identifier">sum</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> 46<span class="keyword">for</span> <span class="special">(</span><span class="keyword">auto</span><span class="special">&&</span> <span class="identifier">x</span> <span class="special">:</span> <span class="identifier">indexed</span><span class="special">(</span><span class="identifier">hist</span><span class="special">)</span><span class="special">)</span> 47 <span class="identifier">sum</span> <span class="special">+=</span> <span class="special">*</span><span class="identifier">x</span><span class="special">;</span> <span class="comment">// dereference accessor</span> 48 49<span class="comment">// or:</span> 50<span class="comment">// auto ind = boost::histogram::indexed(hist);</span> 51<span class="comment">// auto sum = std::accumulate(ind.begin(), ind.end(), 0.0);</span> 52</pre> 53<p> 54 55</p> 56<div class="variablelist"><table border="0" class="variablelist compact"> 57<colgroup> 58<col align="left" valign="top"> 59<col> 60</colgroup> 61<tbody> 62<tr> 63<td><p><span class="term">Parameters:</span></p></td> 64<td><div class="variablelist"><table border="0" class="variablelist compact"> 65<colgroup> 66<col align="left" valign="top"> 67<col> 68</colgroup> 69<tbody> 70<tr> 71<td><p><span class="term"><code class="computeroutput">cov</code></span></p></td> 72<td><p>Iterate over all or only inner bins (optional, default: all). </p></td> 73</tr> 74<tr> 75<td><p><span class="term"><code class="computeroutput">hist</code></span></p></td> 76<td><p>Const reference to the histogram. </p></td> 77</tr> 78</tbody> 79</table></div></td> 80</tr> 81<tr> 82<td><p><span class="term">Returns:</span></p></td> 83<td><p>accumulator type or double</p></td> 84</tr> 85</tbody> 86</table></div> 87</div> 88</div> 89<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 90<td align="left"></td> 91<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Hans 92 Dembinski<p> 93 Distributed under the Boost Software License, Version 1.0. (See accompanying 94 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 95 </p> 96</div></td> 97</tr></table> 98<hr> 99<div class="spirit-nav"> 100<a accesskey="p" href="slice_an_idm45503931040864.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../histogram/reference.html#header.boost.histogram.algorithm.sum_hpp"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../axis/boolean.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 101</div> 102</body> 103</html> 104
