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Next: <a href="Indexing-Cell-Arrays.html" accesskey="n" rel="next">Indexing Cell Arrays</a>, Previous: <a href="Basic-Usage-of-Cell-Arrays.html" accesskey="p" rel="prev">Basic Usage of Cell Arrays</a>, Up: <a href="Cell-Arrays.html" accesskey="u" rel="up">Cell Arrays</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
<h4 class="subsection" id="Creating-Cell-Arrays-1"><span>6.3.2 Creating Cell Arrays<a class="copiable-link" href="#Creating-Cell-Arrays-1"> ¶</a></span></h4>
<p>The introductory example (see <a class="pxref" href="Basic-Usage-of-Cell-Arrays.html">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>
<p>The <code class="code">cell</code> function returns a cell array of a given size, containing
empty matrices. This function is similar to the <code class="code">zeros</code>
function for creating new numerical arrays. The following example creates
a 2-by-2 cell array containing empty matrices
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">c = cell (2,2)
⇒ c =
{
[1,1] = [](0x0)
[2,1] = [](0x0)
[1,2] = [](0x0)
[2,2] = [](0x0)
}
</pre></div></div>
<p>Just like numerical arrays, cell arrays can be multi-dimensional. The
<code class="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
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">c1 = cell (3, 4, 5);
c2 = cell ( [3, 4, 5] );
size (c1)
⇒ ans =
3 4 5
</pre></div></div>
<p>As can be seen, the <a class="ref" href="Object-Sizes.html#XREFsize">size</a> function also works
for cell arrays. As do other functions describing the size of an
object, such as <a class="ref" href="Object-Sizes.html#XREFlength">length</a>, <a class="ref" href="Object-Sizes.html#XREFnumel">numel</a>,
<a class="ref" href="Object-Sizes.html#XREFrows">rows</a>, and <a class="ref" href="Object-Sizes.html#XREFcolumns">columns</a>.
</p>
<a class="anchor" id="XREFcell"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-cell"><span><code class="def-type"><var class="var">C</var> =</code> <strong class="def-name">cell</strong> <code class="def-code-arguments">(<var class="var">n</var>)</code><a class="copiable-link" href="#index-cell"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-cell-1"><span><code class="def-type"><var class="var">C</var> =</code> <strong class="def-name">cell</strong> <code class="def-code-arguments">(<var class="var">m</var>, <var class="var">n</var>)</code><a class="copiable-link" href="#index-cell-1"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-cell-2"><span><code class="def-type"><var class="var">C</var> =</code> <strong class="def-name">cell</strong> <code class="def-code-arguments">(<var class="var">m</var>, <var class="var">n</var>, <var class="var">k</var>, …)</code><a class="copiable-link" href="#index-cell-2"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-cell-3"><span><code class="def-type"><var class="var">C</var> =</code> <strong class="def-name">cell</strong> <code class="def-code-arguments">([<var class="var">m</var> <var class="var">n</var> …])</code><a class="copiable-link" href="#index-cell-3"> ¶</a></span></dt>
<dd><p>Create a new cell array object.
</p>
<p>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>
<p><strong class="strong">See also:</strong> <a class="ref" href="Cell-Arrays-of-Strings.html#XREFcellstr">cellstr</a>, <a class="ref" href="#XREFmat2cell">mat2cell</a>, <a class="ref" href="#XREFnum2cell">num2cell</a>, <a class="ref" href="Processing-Data-in-Structures.html#XREFstruct2cell">struct2cell</a>.
</p></dd></dl>
<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 class="code">num2cell</code>, <code class="code">mat2cell</code> and <code class="code">cellslices</code> functions.
</p>
<a class="anchor" id="XREFnum2cell"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-num2cell"><span><code class="def-type"><var class="var">C</var> =</code> <strong class="def-name">num2cell</strong> <code class="def-code-arguments">(<var class="var">A</var>)</code><a class="copiable-link" href="#index-num2cell"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-num2cell-1"><span><code class="def-type"><var class="var">C</var> =</code> <strong class="def-name">num2cell</strong> <code class="def-code-arguments">(<var class="var">A</var>, <var class="var">dim</var>)</code><a class="copiable-link" href="#index-num2cell-1"> ¶</a></span></dt>
<dd><p>Convert the numeric matrix <var class="var">A</var> to a cell array.
</p>
<p>When no <var class="var">dim</var> is specified, each element of <var class="var">A</var> becomes a 1x1 element
in the output <var class="var">C</var>.
</p>
<p>If <var class="var">dim</var> is defined then individual elements of <var class="var">C</var> contain all of the
elements from <var class="var">A</var> along the specified dimension. <var class="var">dim</var> may also be a
vector of dimensions with the same rule applied.
</p>
<p>For example:
</p>
<div class="example">
<pre class="example-preformatted">x = [1,2;3,4]
⇒
1 2
3 4
## each element of A becomes a 1x1 element of C
num2cell (x)
⇒
{
[1,1] = 1
[2,1] = 3
[1,2] = 2
[2,2] = 4
}
## all rows (dim 1) of A appear in each element of C
num2cell (x, 1)
⇒
{
[1,1] =
1
3
[1,2] =
2
4
}
## all columns (dim 2) of A appear in each element of C
num2cell (x, 2)
⇒
{
[1,1] =
1 2
[2,1] =
3 4
}
## all rows and cols appear in each element of C
## (hence, only 1 output)
num2cell (x, [1, 2])
⇒
{
[1,1] =
1 2
3 4
}
</pre></div>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFmat2cell">mat2cell</a>.
</p></dd></dl>
<a class="anchor" id="XREFmat2cell"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-mat2cell"><span><code class="def-type"><var class="var">C</var> =</code> <strong class="def-name">mat2cell</strong> <code class="def-code-arguments">(<var class="var">A</var>, <var class="var">dim1</var>, <var class="var">dim2</var>, …, <var class="var">dimi</var>, …, <var class="var">dimn</var>)</code><a class="copiable-link" href="#index-mat2cell"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-mat2cell-1"><span><code class="def-type"><var class="var">C</var> =</code> <strong class="def-name">mat2cell</strong> <code class="def-code-arguments">(<var class="var">A</var>, <var class="var">rowdim</var>)</code><a class="copiable-link" href="#index-mat2cell-1"> ¶</a></span></dt>
<dd><p>Convert the matrix <var class="var">A</var> to a cell array <var class="var">C</var>.
</p>
<p>Each dimension argument (<var class="var">dim1</var>, <var class="var">dim2</var>, etc.) is a vector of
integers which specifies how to divide that dimension’s elements amongst the
new elements in the output <var class="var">C</var>. The number of elements in the <var class="var">i</var>-th
dimension is <code class="code">size (<var class="var">A</var>, <var class="var">i</var>)</code>. Because all elements in <var class="var">A</var>
must be partitioned, there is a requirement that <code class="code">sum (<var class="var">dimi</var>) == size
(<var class="var">A</var>, i)</code>. The size of the output cell <var class="var">C</var> is numel (<var class="var">dim1</var>) x
numel (<var class="var">dim2</var>) x … x numel (<var class="var">dimn</var>).
</p>
<p>Given a single dimensional argument, <var class="var">rowdim</var>, the output is divided into
rows as specified. All other dimensions are not divided and thus all
columns (dim 2), pages (dim 3), etc. appear in each output element.
</p>
<p>Examples
</p>
<div class="example">
<pre class="example-preformatted">x = reshape (1:12, [3, 4])'
⇒
1 2 3
4 5 6
7 8 9
10 11 12
</pre><div class="group"><pre class="example-preformatted">## The 4 rows (dim1) are divided in to two cell elements
## with 2 rows each.
## The 3 cols (dim2) are divided in to three cell elements
## with 1 col each.
mat2cell (x, [2,2], [1,1,1])
⇒
{
[1,1] =
1
4
[2,1] =
7
10
[1,2] =
2
5
[2,2] =
8
11
[1,3] =
3
6
[2,3] =
9
12
}
</pre></div><pre class="example-preformatted">
</pre><div class="group"><pre class="example-preformatted">## The 4 rows (dim1) are divided in to two cell elements
## with a 3/1 split.
## All columns appear in each output element.
mat2cell (x, [3,1])
⇒
{
[1,1] =
1 2 3
4 5 6
7 8 9
[2,1] =
10 11 12
}
</pre></div></div>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFnum2cell">num2cell</a>, <a class="ref" href="Processing-Data-in-Cell-Arrays.html#XREFcell2mat">cell2mat</a>.
</p></dd></dl>
<a class="anchor" id="XREFcellslices"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-cellslices"><span><code class="def-type"><var class="var">sl</var> =</code> <strong class="def-name">cellslices</strong> <code class="def-code-arguments">(<var class="var">x</var>, <var class="var">lb</var>, <var class="var">ub</var>, <var class="var">dim</var>)</code><a class="copiable-link" href="#index-cellslices"> ¶</a></span></dt>
<dd><p>Given an array <var class="var">x</var>, this function produces a cell array of slices from
the array determined by the index vectors <var class="var">lb</var>, <var class="var">ub</var>, for lower and
upper bounds, respectively.
</p>
<p>In other words, it is equivalent to the following code:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">n = length (lb);
sl = cell (1, n);
for i = 1:length (lb)
sl{i} = x(:,...,lb(i):ub(i),...,:);
endfor
</pre></div></div>
<p>The position of the index is determined by <var class="var">dim</var>. If not specified,
slicing is done along the first non-singleton dimension.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="Processing-Data-in-Cell-Arrays.html#XREFcell2mat">cell2mat</a>, <a class="ref" href="Indexing-Cell-Arrays.html#XREFcellindexmat">cellindexmat</a>, <a class="ref" href="Function-Application.html#XREFcellfun">cellfun</a>.
</p></dd></dl>
</div>
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