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<p>
Next: <a rel="next" accesskey="n" href="Cell-Arrays-of-Strings.html#Cell-Arrays-of-Strings">Cell Arrays of Strings</a>,
Previous: <a rel="previous" accesskey="p" href="Creating-Cell-Arrays.html#Creating-Cell-Arrays">Creating Cell Arrays</a>,
Up: <a rel="up" accesskey="u" href="Cell-Arrays.html#Cell-Arrays">Cell Arrays</a>
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<h4 class="subsection">6.2.3 Indexing Cell Arrays</h4>
<p>As shown in see <a href="Basic-Usage-of-Cell-Arrays.html#Basic-Usage-of-Cell-Arrays">Basic Usage of Cell Arrays</a> elements can be
extracted from cell arrays using the ‘<samp><span class="samp">{</span></samp>’ and ‘<samp><span class="samp">}</span></samp>’
operators. If you want to extract or access subarrays which are still
cell arrays, you need to use the ‘<samp><span class="samp">(</span></samp>’ and ‘<samp><span class="samp">)</span></samp>’ operators. The
following example illustrates the difference:
<pre class="example"> c = {"1", "2", "3"; "a", "b", "c"; "4", "5", "6"};
c{2,3}
⇒ ans = c
c(2,3)
⇒ ans =
{
[1,1] = c
}
</pre>
<p class="noindent">So with ‘<samp><span class="samp">{}</span></samp>’ you access elements of a cell
array, while with ‘<samp><span class="samp">()</span></samp>’ you access a sub array of a cell
array.
<p>Using the ‘<samp><span class="samp">(</span></samp>’ and ‘<samp><span class="samp">)</span></samp>’ operators, indexing works for cell
arrays like for multi-dimensional arrays. As an example, all the rows
of the first and third column of a cell array can be set to <code>0</code>
with the following command:
<pre class="example"> c(:, [1, 3]) = {0}
⇒ =
{
[1,1] = 0
[2,1] = 0
[3,1] = 0
[1,2] = 2
[2,2] = 10
[3,2] = 20
[1,3] = 0
[2,3] = 0
[3,3] = 0
}
</pre>
<p>Note, that the above can also be achieved like this:
<pre class="example"> c(:, [1, 3]) = 0;
</pre>
<p class="noindent">Here, the scalar ‘<samp><span class="samp">0</span></samp>’ is automatically promoted to
cell array ‘<samp><span class="samp">{0}</span></samp>’ and then assigned to the subarray of <code>c</code>.
<p>To give another example for indexing cell arrays with ‘<samp><span class="samp">()</span></samp>’, you
can exchange the first and the second row of a cell array as in the
following command:
<pre class="example"> c = {1, 2, 3; 4, 5, 6};
c([1, 2], :) = c([2, 1], :)
⇒ =
{
[1,1] = 4
[2,1] = 1
[1,2] = 5
[2,2] = 2
[1,3] = 6
[2,3] = 3
}
</pre>
<p>Accessing multiple elements of a cell array with the ‘<samp><span class="samp">{</span></samp>’ and
‘<samp><span class="samp">}</span></samp>’ operators will result in a comma-separated list of all the
requested elements (see <a href="Comma-Separated-Lists.html#Comma-Separated-Lists">Comma Separated Lists</a>). Using the
‘<samp><span class="samp">{</span></samp>’ and ‘<samp><span class="samp">}</span></samp>’ operators the first two rows in the above
example can be swapped back like this:
<pre class="example"> [c{[1,2], :}] = deal(c{[2, 1], :})
⇒ =
{
[1,1] = 1
[2,1] = 4
[1,2] = 2
[2,2] = 5
[1,3] = 3
[2,3] = 6
}
</pre>
<p>As for struct arrays and numerical arrays, the empty matrix ‘<samp><span class="samp">[]</span></samp>’
can be used to delete elements from a cell array:
<pre class="example"> x = {"1", "2"; "3", "4"};
x(1, :) = []
⇒ x =
{
[1,1] = 3
[1,2] = 4
}
</pre>
<p>The following example shows how to just remove the contents of cell
array elements but not delete the space for them:
<pre class="example"> x = {"1", "2"; "3", "4"};
x{1, :} = []
⇒ x =
{
[1,1] = [](0x0)
[2,1] = 3
[1,2] = [](0x0)
[2,2] = 4
}
</pre>
<p>The indexing operations operate on the cell array and not on the objects
within the cell array. By contrast, <code>cellindexmat</code> applies matrix indexing
to the objects within each cell array entry and returns the requested values.
<!-- cellindexmat src/DLD-FUNCTIONS/cellfun.cc -->
<p><a name="doc_002dcellindexmat"></a>
<div class="defun">
— Loadable Function: <var>y</var> = <b>cellindexmat</b> (<var>x, varargin</var>)<var><a name="index-cellindexmat-469"></a></var><br>
<blockquote><p>Given a cell array of matrices <var>x</var>, this function computes
<pre class="example"> Y = cell (size (X));
for i = 1:numel (X)
Y{i} = X{i}(varargin{:});
endfor
</pre>
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dcellslices.html#doc_002dcellslices">cellslices</a>, <a href="doc_002dcellfun.html#doc_002dcellfun">cellfun</a>.
</p></blockquote></div>
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