File: Histogramming-ntuple-values.html

package info (click to toggle)
gsl-ref-html 2.3-1
  • links: PTS
  • area: non-free
  • in suites: bullseye, buster, sid
  • size: 6,876 kB
  • ctags: 4,574
  • sloc: makefile: 35
file content (133 lines) | stat: -rw-r--r-- 6,562 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016 The GSL Team.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "GNU General Public License" and "Free Software
Needs Free Documentation", the Front-Cover text being "A GNU Manual",
and with the Back-Cover Text being (a) (see below). A copy of the
license is included in the section entitled "GNU Free Documentation
License".

(a) The Back-Cover Text is: "You have the freedom to copy and modify this
GNU Manual." -->
<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ -->
<head>
<title>GNU Scientific Library &ndash; Reference Manual: Histogramming ntuple values</title>

<meta name="description" content="GNU Scientific Library &ndash; Reference Manual: Histogramming ntuple values">
<meta name="keywords" content="GNU Scientific Library &ndash; Reference Manual: Histogramming ntuple values">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link href="index.html#Top" rel="start" title="Top">
<link href="Function-Index.html#Function-Index" rel="index" title="Function Index">
<link href="N_002dtuples.html#N_002dtuples" rel="up" title="N-tuples">
<link href="Example-ntuple-programs.html#Example-ntuple-programs" rel="next" title="Example ntuple programs">
<link href="Closing-an-ntuple-file.html#Closing-an-ntuple-file" rel="previous" title="Closing an ntuple file">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.indentedblock {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
div.smalllisp {margin-left: 3.2em}
kbd {font-style:oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
pre.smalldisplay {font-family: inherit; font-size: smaller}
pre.smallexample {font-size: smaller}
pre.smallformat {font-family: inherit; font-size: smaller}
pre.smalllisp {font-size: smaller}
span.nocodebreak {white-space:nowrap}
span.nolinebreak {white-space:nowrap}
span.roman {font-family:serif; font-weight:normal}
span.sansserif {font-family:sans-serif; font-weight:normal}
ul.no-bullet {list-style: none}
-->
</style>


</head>

<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
<a name="Histogramming-ntuple-values"></a>
<div class="header">
<p>
Next: <a href="Example-ntuple-programs.html#Example-ntuple-programs" accesskey="n" rel="next">Example ntuple programs</a>, Previous: <a href="Closing-an-ntuple-file.html#Closing-an-ntuple-file" accesskey="p" rel="previous">Closing an ntuple file</a>, Up: <a href="N_002dtuples.html#N_002dtuples" accesskey="u" rel="up">N-tuples</a> &nbsp; [<a href="Function-Index.html#Function-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Histogramming-ntuple-values-1"></a>
<h3 class="section">24.7 Histogramming ntuple values</h3>

<p>Once an ntuple has been created its contents can be histogrammed in
various ways using the function <code>gsl_ntuple_project</code>.  Two
user-defined functions must be provided, a function to select events and
a function to compute scalar values. The selection function and the
value function both accept the ntuple row as a first argument and other
parameters as a second argument.
</p>
<a name="index-selection-function_002c-ntuples"></a>
<a name="index-gsl_005fntuple_005fselect_005ffn"></a>
<p>The <em>selection function</em> determines which ntuple rows are selected
for histogramming.  It is defined by the following struct,
</p>
<div class="smallexample">
<pre class="smallexample">typedef struct {
  int (* function) (void * ntuple_data, void * params);
  void * params;
} gsl_ntuple_select_fn;
</pre></div>

<p>The struct component <var>function</var> should return a non-zero value for
each ntuple row that is to be included in the histogram.
</p>
<a name="index-value-function_002c-ntuples"></a>
<a name="index-gsl_005fntuple_005fvalue_005ffn"></a>
<p>The <em>value function</em> computes scalar values for those ntuple rows
selected by the selection function,
</p>
<div class="smallexample">
<pre class="smallexample">typedef struct {
  double (* function) (void * ntuple_data, void * params);
  void * params;
} gsl_ntuple_value_fn;
</pre></div>

<p>In this case the struct component <var>function</var> should return the value
to be added to the histogram for the ntuple row.  
</p>
<a name="index-histogram_002c-from-ntuple"></a>
<a name="index-projection-of-ntuples"></a>
<dl>
<dt><a name="index-gsl_005fntuple_005fproject"></a>Function: <em>int</em> <strong>gsl_ntuple_project</strong> <em>(gsl_histogram * <var>h</var>, gsl_ntuple * <var>ntuple</var>, gsl_ntuple_value_fn * <var>value_func</var>, gsl_ntuple_select_fn * <var>select_func</var>)</em></dt>
<dd><p>This function updates the histogram <var>h</var> from the ntuple <var>ntuple</var>
using the functions <var>value_func</var> and <var>select_func</var>. For each
ntuple row where the selection function <var>select_func</var> is non-zero the
corresponding value of that row is computed using the function
<var>value_func</var> and added to the histogram.  Those ntuple rows where
<var>select_func</var> returns zero are ignored.  New entries are added to
the histogram, so subsequent calls can be used to accumulate further
data in the same histogram.
</p></dd></dl>

<hr>
<div class="header">
<p>
Next: <a href="Example-ntuple-programs.html#Example-ntuple-programs" accesskey="n" rel="next">Example ntuple programs</a>, Previous: <a href="Closing-an-ntuple-file.html#Closing-an-ntuple-file" accesskey="p" rel="previous">Closing an ntuple file</a>, Up: <a href="N_002dtuples.html#N_002dtuples" accesskey="u" rel="up">N-tuples</a> &nbsp; [<a href="Function-Index.html#Function-Index" title="Index" rel="index">Index</a>]</p>
</div>



</body>
</html>