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
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
|
<html lang="en">
<head>
<title>Matrix views - GNU Scientific Library -- Reference Manual</title>
<meta http-equiv="Content-Type" content="text/html">
<meta name="description" content="GNU Scientific Library -- Reference Manual">
<meta name="generator" content="makeinfo 4.8">
<link title="Top" rel="start" href="index.html#Top">
<link rel="up" href="Matrices.html" title="Matrices">
<link rel="prev" href="Reading-and-writing-matrices.html" title="Reading and writing matrices">
<link rel="next" href="Creating-row-and-column-views.html" title="Creating row and column views">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
<!--
Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 The GSL Team.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2 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 freedom to copy and modify this
GNU Manual, like GNU software.''-->
<meta http-equiv="Content-Style-Type" content="text/css">
<style type="text/css"><!--
pre.display { font-family:inherit }
pre.format { font-family:inherit }
pre.smalldisplay { font-family:inherit; font-size:smaller }
pre.smallformat { font-family:inherit; font-size:smaller }
pre.smallexample { font-size:smaller }
pre.smalllisp { font-size:smaller }
span.sc { font-variant:small-caps }
span.roman { font-family:serif; font-weight:normal; }
span.sansserif { font-family:sans-serif; font-weight:normal; }
--></style>
</head>
<body>
<div class="node">
<p>
<a name="Matrix-views"></a>
Next: <a rel="next" accesskey="n" href="Creating-row-and-column-views.html">Creating row and column views</a>,
Previous: <a rel="previous" accesskey="p" href="Reading-and-writing-matrices.html">Reading and writing matrices</a>,
Up: <a rel="up" accesskey="u" href="Matrices.html">Matrices</a>
<hr>
</div>
<h4 class="subsection">8.4.5 Matrix views</h4>
<p>A matrix view is a temporary object, stored on the stack, which can be
used to operate on a subset of matrix elements. Matrix views can be
defined for both constant and non-constant matrices using separate types
that preserve constness. A matrix view has the type
<code>gsl_matrix_view</code> and a constant matrix view has the type
<code>gsl_matrix_const_view</code>. In both cases the elements of the view
can by accessed using the <code>matrix</code> component of the view object. A
pointer <code>gsl_matrix *</code> or <code>const gsl_matrix *</code> can be obtained
by taking the address of the <code>matrix</code> component with the <code>&</code>
operator. In addition to matrix views it is also possible to create
vector views of a matrix, such as row or column views.
<div class="defun">
— Function: gsl_matrix_view <b>gsl_matrix_submatrix</b> (<var>gsl_matrix * m, size_t k1, size_t k2, size_t n1, size_t n2</var>)<var><a name="index-gsl_005fmatrix_005fsubmatrix-935"></a></var><br>
— Function: gsl_matrix_const_view <b>gsl_matrix_const_submatrix</b> (<var>const gsl_matrix * m, size_t k1, size_t k2, size_t n1, size_t n2</var>)<var><a name="index-gsl_005fmatrix_005fconst_005fsubmatrix-936"></a></var><br>
<blockquote><p>These functions return a matrix view of a submatrix of the matrix
<var>m</var>. The upper-left element of the submatrix is the element
(<var>k1</var>,<var>k2</var>) of the original matrix. The submatrix has <var>n1</var>
rows and <var>n2</var> columns. The physical number of columns in memory
given by <var>tda</var> is unchanged. Mathematically, the
(i,j)-th element of the new matrix is given by,
<pre class="example"> m'(i,j) = m->data[(k1*m->tda + k2) + i*m->tda + j]
</pre>
<p class="noindent">where the index <var>i</var> runs from 0 to <code>n1-1</code> and the index <var>j</var>
runs from 0 to <code>n2-1</code>.
<p>The <code>data</code> pointer of the returned matrix struct is set to null if
the combined parameters (<var>i</var>,<var>j</var>,<var>n1</var>,<var>n2</var>,<var>tda</var>)
overrun the ends of the original matrix.
<p>The new matrix view is only a view of the block underlying the existing
matrix, <var>m</var>. The block containing the elements of <var>m</var> is not
owned by the new matrix view. When the view goes out of scope the
original matrix <var>m</var> and its block will continue to exist. The
original memory can only be deallocated by freeing the original matrix.
Of course, the original matrix should not be deallocated while the view
is still in use.
<p>The function <code>gsl_matrix_const_submatrix</code> is equivalent to
<code>gsl_matrix_submatrix</code> but can be used for matrices which are
declared <code>const</code>.
</p></blockquote></div>
<div class="defun">
— Function: gsl_matrix_view <b>gsl_matrix_view_array</b> (<var>double * base, size_t n1, size_t n2</var>)<var><a name="index-gsl_005fmatrix_005fview_005farray-937"></a></var><br>
— Function: gsl_matrix_const_view <b>gsl_matrix_const_view_array</b> (<var>const double * base, size_t n1, size_t n2</var>)<var><a name="index-gsl_005fmatrix_005fconst_005fview_005farray-938"></a></var><br>
<blockquote><p>These functions return a matrix view of the array <var>base</var>. The
matrix has <var>n1</var> rows and <var>n2</var> columns. The physical number of
columns in memory is also given by <var>n2</var>. Mathematically, the
(i,j)-th element of the new matrix is given by,
<pre class="example"> m'(i,j) = base[i*n2 + j]
</pre>
<p class="noindent">where the index <var>i</var> runs from 0 to <code>n1-1</code> and the index <var>j</var>
runs from 0 to <code>n2-1</code>.
<p>The new matrix is only a view of the array <var>base</var>. When the view
goes out of scope the original array <var>base</var> will continue to exist.
The original memory can only be deallocated by freeing the original
array. Of course, the original array should not be deallocated while
the view is still in use.
<p>The function <code>gsl_matrix_const_view_array</code> is equivalent to
<code>gsl_matrix_view_array</code> but can be used for matrices which are
declared <code>const</code>.
</p></blockquote></div>
<div class="defun">
— Function: gsl_matrix_view <b>gsl_matrix_view_array_with_tda</b> (<var>double * base, size_t n1, size_t n2, size_t tda</var>)<var><a name="index-gsl_005fmatrix_005fview_005farray_005fwith_005ftda-939"></a></var><br>
— Function: gsl_matrix_const_view <b>gsl_matrix_const_view_array_with_tda</b> (<var>const double * base, size_t n1, size_t n2, size_t tda</var>)<var><a name="index-gsl_005fmatrix_005fconst_005fview_005farray_005fwith_005ftda-940"></a></var><br>
<blockquote><p>These functions return a matrix view of the array <var>base</var> with a
physical number of columns <var>tda</var> which may differ from the corresponding
dimension of the matrix. The matrix has <var>n1</var> rows and <var>n2</var>
columns, and the physical number of columns in memory is given by
<var>tda</var>. Mathematically, the (i,j)-th element of the new
matrix is given by,
<pre class="example"> m'(i,j) = base[i*tda + j]
</pre>
<p class="noindent">where the index <var>i</var> runs from 0 to <code>n1-1</code> and the index <var>j</var>
runs from 0 to <code>n2-1</code>.
<p>The new matrix is only a view of the array <var>base</var>. When the view
goes out of scope the original array <var>base</var> will continue to exist.
The original memory can only be deallocated by freeing the original
array. Of course, the original array should not be deallocated while
the view is still in use.
<p>The function <code>gsl_matrix_const_view_array_with_tda</code> is equivalent
to <code>gsl_matrix_view_array_with_tda</code> but can be used for matrices
which are declared <code>const</code>.
</p></blockquote></div>
<div class="defun">
— Function: gsl_matrix_view <b>gsl_matrix_view_vector</b> (<var>gsl_vector * v, size_t n1, size_t n2</var>)<var><a name="index-gsl_005fmatrix_005fview_005fvector-941"></a></var><br>
— Function: gsl_matrix_const_view <b>gsl_matrix_const_view_vector</b> (<var>const gsl_vector * v, size_t n1, size_t n2</var>)<var><a name="index-gsl_005fmatrix_005fconst_005fview_005fvector-942"></a></var><br>
<blockquote><p>These functions return a matrix view of the vector <var>v</var>. The matrix
has <var>n1</var> rows and <var>n2</var> columns. The vector must have unit
stride. The physical number of columns in memory is also given by
<var>n2</var>. Mathematically, the (i,j)-th element of the new
matrix is given by,
<pre class="example"> m'(i,j) = v->data[i*n2 + j]
</pre>
<p class="noindent">where the index <var>i</var> runs from 0 to <code>n1-1</code> and the index <var>j</var>
runs from 0 to <code>n2-1</code>.
<p>The new matrix is only a view of the vector <var>v</var>. When the view
goes out of scope the original vector <var>v</var> will continue to exist.
The original memory can only be deallocated by freeing the original
vector. Of course, the original vector should not be deallocated while
the view is still in use.
<p>The function <code>gsl_matrix_const_view_vector</code> is equivalent to
<code>gsl_matrix_view_vector</code> but can be used for matrices which are
declared <code>const</code>.
</p></blockquote></div>
<div class="defun">
— Function: gsl_matrix_view <b>gsl_matrix_view_vector_with_tda</b> (<var>gsl_vector * v, size_t n1, size_t n2, size_t tda</var>)<var><a name="index-gsl_005fmatrix_005fview_005fvector_005fwith_005ftda-943"></a></var><br>
— Function: gsl_matrix_const_view <b>gsl_matrix_const_view_vector_with_tda</b> (<var>const gsl_vector * v, size_t n1, size_t n2, size_t tda</var>)<var><a name="index-gsl_005fmatrix_005fconst_005fview_005fvector_005fwith_005ftda-944"></a></var><br>
<blockquote><p>These functions return a matrix view of the vector <var>v</var> with a
physical number of columns <var>tda</var> which may differ from the
corresponding matrix dimension. The vector must have unit stride. The
matrix has <var>n1</var> rows and <var>n2</var> columns, and the physical number
of columns in memory is given by <var>tda</var>. Mathematically, the
(i,j)-th element of the new matrix is given by,
<pre class="example"> m'(i,j) = v->data[i*tda + j]
</pre>
<p class="noindent">where the index <var>i</var> runs from 0 to <code>n1-1</code> and the index <var>j</var>
runs from 0 to <code>n2-1</code>.
<p>The new matrix is only a view of the vector <var>v</var>. When the view
goes out of scope the original vector <var>v</var> will continue to exist.
The original memory can only be deallocated by freeing the original
vector. Of course, the original vector should not be deallocated while
the view is still in use.
<p>The function <code>gsl_matrix_const_view_vector_with_tda</code> is equivalent
to <code>gsl_matrix_view_vector_with_tda</code> but can be used for matrices
which are declared <code>const</code>.
</p></blockquote></div>
<!-- @node Modifying matrix views -->
<!-- @subsection Modifying matrix views -->
<!-- @deftypefun int gsl_matrix_view_from_matrix (gsl_matrix * @var{m}, gsl_matrix * @var{mm}, const size_t @var{k1}, const size_t @var{k2}, const size_t @var{n1}, const size_t @var{n2}) -->
<!-- This function modifies and existing matrix view @var{m} to form a new -->
<!-- view of a matrix @var{mm}, starting from element (@var{k1},@var{k2}). -->
<!-- The matrix view has @var{n1} rows and @var{n2} columns. Any existing -->
<!-- view in @var{m} will be lost as a result of this function. -->
<!-- @end deftypefun -->
<!-- @deftypefun int gsl_matrix_view_from_vector (gsl_matrix * @var{m}, gsl_vector * @var{v}, const size_t @var{offset}, const size_t @var{n1}, const size_t @var{n2}) -->
<!-- This function modifies and existing matrix view @var{m} to form a new -->
<!-- view of a vector @var{v}, starting from element @var{offset}. The -->
<!-- vector has @var{n1} rows and @var{n2} columns. Any -->
<!-- existing view in @var{m} will be lost as a result of this function. -->
<!-- @end deftypefun -->
<!-- @deftypefun int gsl_matrix_view_from_array (gsl_matrix * @var{m}, double * @var{base}, const size_t @var{offset}, const size_t @var{n1}, const size_t @var{n2}) -->
<!-- This function modifies and existing matrix view @var{m} to form a new -->
<!-- view of an array @var{base}, starting from element @var{offset}. The -->
<!-- matrix has @var{n1} rows and @var{n2} columns. Any -->
<!-- existing view in @var{m} will be lost as a result of this function. -->
<!-- @end deftypefun -->
<!-- @deftypefun {gsl_matrix *} gsl_matrix_alloc_from_block (gsl_block * @var{b}, size_t @var{offset}, size_t @var{n1}, size_t @var{n2}, size_t @var{tda}) -->
<!-- This function creates a matrix as a slice of the block @var{b}, -->
<!-- returning a pointer to a newly initialized matrix struct. The start of -->
<!-- the matrix is offset by @var{offset} elements from the start of the -->
<!-- block. The matrix has @var{n1} rows and @var{n2} columns, with the -->
<!-- physical number of columns in memory given by @var{tda}. -->
<!-- Mathematically, the (@var{i},@var{j})-th element of the matrix is given by, -->
<!-- @example -->
<!-- m(i,j) = b->data[offset + i*tda + j] -->
<!-- @end example -->
<!-- @noindent -->
<!-- where the index @var{i} runs from 0 to @code{n1-1} and the index @var{j} -->
<!-- runs from 0 to @code{n2-1}. -->
<!-- A null pointer is returned if the combined parameters -->
<!-- (@var{offset},@var{n1},@var{n2},@var{tda}) overrun the end of the block -->
<!-- or if insufficient memory is available to store the matrix. -->
<!-- The matrix is only a view of the block @var{b}, and the block is not -->
<!-- owned by the matrix. When the matrix is deallocated the block @var{b} -->
<!-- will continue to exist. This memory can only be deallocated by freeing -->
<!-- the block itself. Of course, this block should not be deallocated while -->
<!-- the matrix is still in use. -->
<!-- @end deftypefun -->
<!-- @deftypefun {gsl_matrix *} gsl_matrix_alloc_from_matrix (gsl_matrix * @var{m}, size_t @var{k1}, size_t @var{k2}, size_t @var{n1}, size_t @var{n2}) -->
<!-- This function creates a matrix as a submatrix of the matrix @var{m}, -->
<!-- returning a pointer to a newly initialized matrix struct. The upper-left -->
<!-- element of the submatrix is the element (@var{k1},@var{k2}) of the -->
<!-- original matrix. The submatrix has @var{n1} rows and @var{n2} columns. -->
<!-- The physical number of columns in memory given by @var{tda} is -->
<!-- unchanged. Mathematically, the (@var{i},@var{j})-th element of the -->
<!-- new matrix is given by, -->
<!-- @example -->
<!-- m'(i,j) = m->data[(k1*m->tda + k2) + i*m->tda + j] -->
<!-- @end example -->
<!-- @noindent -->
<!-- where the index @var{i} runs from 0 to @code{n1-1} and the index @var{j} -->
<!-- runs from 0 to @code{n2-1}. -->
<!-- A null pointer is returned if the combined parameters -->
<!-- (@var{k1},@var{k2},@var{n1},@var{n2},@var{tda}) overrun the end of the -->
<!-- original matrix or if insufficient memory is available to store the matrix. -->
<!-- The new matrix is only a view of the block underlying the existing -->
<!-- matrix, @var{m}. The block is not owned by the new matrix. When the new -->
<!-- matrix is deallocated the original matrix @var{m} and its block will -->
<!-- continue to exist. The original memory can only be deallocated by -->
<!-- freeing the original matrix. Of course, the original matrix should not -->
<!-- be deallocated while the new matrix is still in use. -->
<!-- @end deftypefun -->
</body></html>
|
