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<title>GNU Scientific Library – Reference Manual: Creating row and column views</title>
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<a name="Creating-row-and-column-views"></a>
<div class="header">
<p>
Next: <a href="Copying-matrices.html#Copying-matrices" accesskey="n" rel="next">Copying matrices</a>, Previous: <a href="Matrix-views.html#Matrix-views" accesskey="p" rel="previous">Matrix views</a>, Up: <a href="Matrices.html#Matrices" accesskey="u" rel="up">Matrices</a> [<a href="Function-Index.html#Function-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Creating-row-and-column-views-1"></a>
<h4 class="subsection">8.4.6 Creating row and column views</h4>
<p>In general there are two ways to access an object, by reference or by
copying. The functions described in this section create vector views
which allow access to a row or column of a matrix by reference.
Modifying elements of the view is equivalent to modifying the matrix,
since both the vector view and the matrix point to the same memory
block.
</p>
<dl>
<dt><a name="index-gsl_005fmatrix_005frow"></a>Function: <em>gsl_vector_view</em> <strong>gsl_matrix_row</strong> <em>(gsl_matrix * <var>m</var>, size_t <var>i</var>)</em></dt>
<dt><a name="index-gsl_005fmatrix_005fconst_005frow"></a>Function: <em>gsl_vector_const_view</em> <strong>gsl_matrix_const_row</strong> <em>(const gsl_matrix * <var>m</var>, size_t <var>i</var>)</em></dt>
<dd><p>These functions return a vector view of the <var>i</var>-th row of the matrix
<var>m</var>. The <code>data</code> pointer of the new vector is set to null if
<var>i</var> is out of range.
</p>
<p>The function <code>gsl_vector_const_row</code> is equivalent to
<code>gsl_matrix_row</code> but can be used for matrices which are declared
<code>const</code>.
</p></dd></dl>
<dl>
<dt><a name="index-gsl_005fmatrix_005fcolumn"></a>Function: <em>gsl_vector_view</em> <strong>gsl_matrix_column</strong> <em>(gsl_matrix * <var>m</var>, size_t <var>j</var>)</em></dt>
<dt><a name="index-gsl_005fmatrix_005fconst_005fcolumn"></a>Function: <em>gsl_vector_const_view</em> <strong>gsl_matrix_const_column</strong> <em>(const gsl_matrix * <var>m</var>, size_t <var>j</var>)</em></dt>
<dd><p>These functions return a vector view of the <var>j</var>-th column of the
matrix <var>m</var>. The <code>data</code> pointer of the new vector is set to
null if <var>j</var> is out of range.
</p>
<p>The function <code>gsl_vector_const_column</code> is equivalent to
<code>gsl_matrix_column</code> but can be used for matrices which are declared
<code>const</code>.
</p></dd></dl>
<dl>
<dt><a name="index-gsl_005fmatrix_005fsubrow"></a>Function: <em>gsl_vector_view</em> <strong>gsl_matrix_subrow</strong> <em>(gsl_matrix * <var>m</var>, size_t <var>i</var>, size_t <var>offset</var>, size_t <var>n</var>)</em></dt>
<dt><a name="index-gsl_005fmatrix_005fconst_005fsubrow"></a>Function: <em>gsl_vector_const_view</em> <strong>gsl_matrix_const_subrow</strong> <em>(const gsl_matrix * <var>m</var>, size_t <var>i</var>, size_t <var>offset</var>, size_t <var>n</var>)</em></dt>
<dd><p>These functions return a vector view of the <var>i</var>-th row of the matrix
<var>m</var> beginning at <var>offset</var> elements past the first column and
containing <var>n</var> elements. The <code>data</code> pointer of the new vector
is set to null if <var>i</var>, <var>offset</var>, or <var>n</var> are out of range.
</p>
<p>The function <code>gsl_vector_const_subrow</code> is equivalent to
<code>gsl_matrix_subrow</code> but can be used for matrices which are declared
<code>const</code>.
</p></dd></dl>
<dl>
<dt><a name="index-gsl_005fmatrix_005fsubcolumn"></a>Function: <em>gsl_vector_view</em> <strong>gsl_matrix_subcolumn</strong> <em>(gsl_matrix * <var>m</var>, size_t <var>j</var>, size_t <var>offset</var>, size_t <var>n</var>)</em></dt>
<dt><a name="index-gsl_005fmatrix_005fconst_005fsubcolumn"></a>Function: <em>gsl_vector_const_view</em> <strong>gsl_matrix_const_subcolumn</strong> <em>(const gsl_matrix * <var>m</var>, size_t <var>j</var>, size_t <var>offset</var>, size_t <var>n</var>)</em></dt>
<dd><p>These functions return a vector view of the <var>j</var>-th column of the matrix
<var>m</var> beginning at <var>offset</var> elements past the first row and
containing <var>n</var> elements. The <code>data</code> pointer of the new vector
is set to null if <var>j</var>, <var>offset</var>, or <var>n</var> are out of range.
</p>
<p>The function <code>gsl_vector_const_subcolumn</code> is equivalent to
<code>gsl_matrix_subcolumn</code> but can be used for matrices which are declared
<code>const</code>.
</p></dd></dl>
<a name="index-matrix-diagonal"></a>
<a name="index-diagonal_002c-of-a-matrix"></a>
<dl>
<dt><a name="index-gsl_005fmatrix_005fdiagonal"></a>Function: <em>gsl_vector_view</em> <strong>gsl_matrix_diagonal</strong> <em>(gsl_matrix * <var>m</var>)</em></dt>
<dt><a name="index-gsl_005fmatrix_005fconst_005fdiagonal"></a>Function: <em>gsl_vector_const_view</em> <strong>gsl_matrix_const_diagonal</strong> <em>(const gsl_matrix * <var>m</var>)</em></dt>
<dd><p>These functions return a vector view of the diagonal of the matrix
<var>m</var>. The matrix <var>m</var> is not required to be square. For a
rectangular matrix the length of the diagonal is the same as the smaller
dimension of the matrix.
</p>
<p>The function <code>gsl_matrix_const_diagonal</code> is equivalent to
<code>gsl_matrix_diagonal</code> but can be used for matrices which are
declared <code>const</code>.
</p></dd></dl>
<a name="index-matrix-subdiagonal"></a>
<a name="index-subdiagonal_002c-of-a-matrix"></a>
<dl>
<dt><a name="index-gsl_005fmatrix_005fsubdiagonal"></a>Function: <em>gsl_vector_view</em> <strong>gsl_matrix_subdiagonal</strong> <em>(gsl_matrix * <var>m</var>, size_t <var>k</var>) </em></dt>
<dt><a name="index-gsl_005fmatrix_005fconst_005fsubdiagonal"></a>Function: <em>gsl_vector_const_view</em> <strong>gsl_matrix_const_subdiagonal</strong> <em>(const gsl_matrix * <var>m</var>, size_t <var>k</var>)</em></dt>
<dd><p>These functions return a vector view of the <var>k</var>-th subdiagonal of
the matrix <var>m</var>. The matrix <var>m</var> is not required to be square.
The diagonal of the matrix corresponds to <em>k = 0</em>.
</p>
<p>The function <code>gsl_matrix_const_subdiagonal</code> is equivalent to
<code>gsl_matrix_subdiagonal</code> but can be used for matrices which are
declared <code>const</code>.
</p></dd></dl>
<a name="index-matrix-superdiagonal"></a>
<a name="index-superdiagonal_002c-matrix"></a>
<dl>
<dt><a name="index-gsl_005fmatrix_005fsuperdiagonal"></a>Function: <em>gsl_vector_view</em> <strong>gsl_matrix_superdiagonal</strong> <em>(gsl_matrix * <var>m</var>, size_t <var>k</var>) </em></dt>
<dt><a name="index-gsl_005fmatrix_005fconst_005fsuperdiagonal"></a>Function: <em>gsl_vector_const_view</em> <strong>gsl_matrix_const_superdiagonal</strong> <em>(const gsl_matrix * <var>m</var>, size_t <var>k</var>)</em></dt>
<dd><p>These functions return a vector view of the <var>k</var>-th superdiagonal of
the matrix <var>m</var>. The matrix <var>m</var> is not required to be square. The
diagonal of the matrix corresponds to <em>k = 0</em>.
</p>
<p>The function <code>gsl_matrix_const_superdiagonal</code> is equivalent to
<code>gsl_matrix_superdiagonal</code> but can be used for matrices which are
declared <code>const</code>.
</p></dd></dl>
<hr>
<div class="header">
<p>
Next: <a href="Copying-matrices.html#Copying-matrices" accesskey="n" rel="next">Copying matrices</a>, Previous: <a href="Matrix-views.html#Matrix-views" accesskey="p" rel="previous">Matrix views</a>, Up: <a href="Matrices.html#Matrices" accesskey="u" rel="up">Matrices</a> [<a href="Function-Index.html#Function-Index" title="Index" rel="index">Index</a>]</p>
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