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<html lang="en">
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<title>Creating Cell Arrays - GNU Octave</title>
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<p>
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Previous: <a rel="previous" accesskey="p" href="Basic-Usage-of-Cell-Arrays.html#Basic-Usage-of-Cell-Arrays">Basic Usage of Cell Arrays</a>,
Up: <a rel="up" accesskey="u" href="Cell-Arrays.html#Cell-Arrays">Cell Arrays</a>
<hr>
</div>
<h4 class="subsection">6.2.2 Creating Cell Array</h4>
<p>The introductory example (see <a href="Basic-Usage-of-Cell-Arrays.html#Basic-Usage-of-Cell-Arrays">Basic Usage of Cell Arrays</a>) showed
how to create a cell array containing currently available variables.
In many situations, however, it is useful to create a cell array and
then fill it with data.
<p>The <code>cell</code> function returns a cell array of a given size, containing
empty matrices. This function is similar to the <code>zeros</code>
function for creating new numerical arrays. The following example creates
a 2-by-2 cell array containing empty matrices
<pre class="example"> c = cell(2,2)
⇒ c =
{
[1,1] = [](0x0)
[2,1] = [](0x0)
[1,2] = [](0x0)
[2,2] = [](0x0)
}
</pre>
<p>Just like numerical arrays, cell arrays can be multi-dimensional. The
<code>cell</code> function accepts any number of positive integers to describe
the size of the returned cell array. It is also possible to set the size
of the cell array through a vector of positive integers. In the
following example two cell arrays of equal size are created, and the size
of the first one is displayed
<pre class="example"> c1 = cell(3, 4, 5);
c2 = cell( [3, 4, 5] );
size(c1)
⇒ ans =
3 4 5
</pre>
<p class="noindent">As can be seen, the <a href="doc_002dsize.html#doc_002dsize"><code>size</code></a> function also works
for cell arrays. As do other functions describing the size of an
object, such as <a href="doc_002dlength.html#doc_002dlength"><code>length</code></a>, <a href="doc_002dnumel.html#doc_002dnumel"><code>numel</code></a>, <a href="doc_002drows.html#doc_002drows"><code>rows</code></a>, and <a href="doc_002dcolumns.html#doc_002dcolumns"><code>columns</code></a>.
<!-- cell src/ov-cell.cc -->
<p><a name="doc_002dcell"></a>
<div class="defun">
— Built-in Function: <b>cell</b> (<var>n</var>)<var><a name="index-cell-459"></a></var><br>
— Built-in Function: <b>cell</b> (<var>m, n</var>)<var><a name="index-cell-460"></a></var><br>
— Built-in Function: <b>cell</b> (<var>m, n, k, <small class="dots">...</small></var>)<var><a name="index-cell-461"></a></var><br>
— Built-in Function: <b>cell</b> ([<var>m n <small class="dots">...</small></var>])<var><a name="index-cell-462"></a></var><br>
<blockquote><p>Create a new cell array object.
If invoked with a single scalar integer argument, return a square
NxN cell array. If invoked with two or more scalar
integer arguments, or a vector of integer values, return an array with
the given dimensions.
</p></blockquote></div>
<p>As an alternative to creating empty cell arrays, and then filling them, it
is possible to convert numerical arrays into cell arrays using the
<code>num2cell</code>, <code>mat2cell</code> and <code>cellslices</code> functions.
<!-- num2cell src/DLD-FUNCTIONS/cellfun.cc -->
<p><a name="doc_002dnum2cell"></a>
<div class="defun">
— Loadable Function: <var>C</var> = <b>num2cell</b> (<var>A</var>)<var><a name="index-num2cell-463"></a></var><br>
— Loadable Function: <var>C</var> = <b>num2cell</b> (<var>A, dim</var>)<var><a name="index-num2cell-464"></a></var><br>
<blockquote><p>Convert the numeric matrix <var>A</var> to a cell array. If <var>dim</var> is
defined, the value <var>C</var> is of dimension 1 in this dimension and the
elements of <var>A</var> are placed into <var>C</var> in slices. For example:
<pre class="example"> num2cell([1,2;3,4])
⇒ ans =
{
[1,1] = 1
[2,1] = 3
[1,2] = 2
[2,2] = 4
}
num2cell([1,2;3,4],1)
⇒ ans =
{
[1,1] =
1
3
[1,2] =
2
4
}
</pre>
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dmat2cell.html#doc_002dmat2cell">mat2cell</a>.
</p></blockquote></div>
<!-- mat2cell src/DLD-FUNCTIONS/cellfun.cc -->
<p><a name="doc_002dmat2cell"></a>
<div class="defun">
— Loadable Function: <var>C</var> = <b>mat2cell</b> (<var>A, m, n</var>)<var><a name="index-mat2cell-465"></a></var><br>
— Loadable Function: <var>C</var> = <b>mat2cell</b> (<var>A, d1, d2, <small class="dots">...</small></var>)<var><a name="index-mat2cell-466"></a></var><br>
— Loadable Function: <var>C</var> = <b>mat2cell</b> (<var>A, r</var>)<var><a name="index-mat2cell-467"></a></var><br>
<blockquote><p>Convert the matrix <var>A</var> to a cell array. If <var>A</var> is 2-D, then
it is required that <code>sum (</code><var>m</var><code>) == size (</code><var>A</var><code>, 1)</code> and
<code>sum (</code><var>n</var><code>) == size (</code><var>A</var><code>, 2)</code>. Similarly, if <var>A</var> is
multi-dimensional and the number of dimensional arguments is equal
to the dimensions of <var>A</var>, then it is required that <code>sum (</code><var>di</var><code>)
== size (</code><var>A</var><code>, i)</code>.
<p>Given a single dimensional argument <var>r</var>, the other dimensional
arguments are assumed to equal <code>size (</code><var>A</var><code>,</code><var>i</var><code>)</code>.
<p>An example of the use of mat2cell is
<pre class="example"> mat2cell (reshape(1:16,4,4),[3,1],[3,1])
⇒ {
[1,1] =
1 5 9
2 6 10
3 7 11
[2,1] =
4 8 12
[1,2] =
13
14
15
[2,2] = 16
}
</pre>
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dnum2cell.html#doc_002dnum2cell">num2cell</a>, <a href="doc_002dcell2mat.html#doc_002dcell2mat">cell2mat</a>.
</p></blockquote></div>
<!-- cellslices src/DLD-FUNCTIONS/cellfun.cc -->
<p><a name="doc_002dcellslices"></a>
<div class="defun">
— Loadable Function: <var>sl</var> = <b>cellslices</b> (<var>x, lb, ub, dim</var>)<var><a name="index-cellslices-468"></a></var><br>
<blockquote><p>Given an array <var>x</var>, this function produces a cell array of slices from
the array determined by the index vectors <var>lb</var>, <var>ub</var>, for lower and
upper bounds, respectively. In other words, it is equivalent to the
following code:
<pre class="example"> n = length (lb);
sl = cell (1, n);
for i = 1:length (lb)
sl{i} = x(:,...,lb(i):ub(i),...,:);
endfor
</pre>
<p>The position of the index is determined by <var>dim</var>. If not specified,
slicing is done along the first non-singleton dimension.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dcell2mat.html#doc_002dcell2mat">cell2mat</a>, <a href="doc_002dcellindexmat.html#doc_002dcellindexmat">cellindexmat</a>, <a href="doc_002dcellfun.html#doc_002dcellfun">cellfun</a>.
</p></blockquote></div>
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