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<a name="Processing-Data-in-Cell-Arrays"></a>
<p>
Previous: <a rel="previous" accesskey="p" href="Cell-Arrays-of-Strings.html#Cell-Arrays-of-Strings">Cell Arrays of Strings</a>,
Up: <a rel="up" accesskey="u" href="Cell-Arrays.html#Cell-Arrays">Cell Arrays</a>
<hr>
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<h4 class="subsection">6.2.5 Processing Data in Cell Arrays</h4>
<p>Data that is stored in a cell array can be processed in several ways
depending on the actual data. The simplest way to process that data
is to iterate through it using one or more <code>for</code> loops. The same
idea can be implemented more easily through the use of the <code>cellfun</code>
function that calls a user-specified function on all elements of a cell
array.
<!-- ./DLD-FUNCTIONS/cellfun.cc -->
<p><a name="doc_002dcellfun"></a>
<div class="defun">
— Loadable Function: <b>cellfun</b> (<var>name, c</var>)<var><a name="index-cellfun-400"></a></var><br>
— Loadable Function: <b>cellfun</b> (<var>"size", c, k</var>)<var><a name="index-cellfun-401"></a></var><br>
— Loadable Function: <b>cellfun</b> (<var>"isclass", c, class</var>)<var><a name="index-cellfun-402"></a></var><br>
— Loadable Function: <b>cellfun</b> (<var>func, c</var>)<var><a name="index-cellfun-403"></a></var><br>
— Loadable Function: <b>cellfun</b> (<var>func, c, d</var>)<var><a name="index-cellfun-404"></a></var><br>
— Loadable Function: [<var>a</var>, <var>b</var>] = <b>cellfun</b> (<var><small class="dots">...</small></var>)<var><a name="index-cellfun-405"></a></var><br>
— Loadable Function: <b>cellfun</b> (<var><small class="dots">...</small>, 'ErrorHandler', errfunc</var>)<var><a name="index-cellfun-406"></a></var><br>
— Loadable Function: <b>cellfun</b> (<var><small class="dots">...</small>, 'UniformOutput', val</var>)<var><a name="index-cellfun-407"></a></var><br>
<blockquote>
<p>Evaluate the function named <var>name</var> on the elements of the cell array
<var>c</var>. Elements in <var>c</var> are passed on to the named function
individually. The function <var>name</var> can be one of the functions
<dl>
<dt><code>isempty</code><dd>Return 1 for empty elements.
<br><dt><code>islogical</code><dd>Return 1 for logical elements.
<br><dt><code>isreal</code><dd>Return 1 for real elements.
<br><dt><code>length</code><dd>Return a vector of the lengths of cell elements.
<br><dt><code>ndims</code><dd>Return the number of dimensions of each element.
<br><dt><code>prodofsize</code><dd>Return the product of dimensions of each element.
<br><dt><code>size</code><dd>Return the size along the <var>k</var>-th dimension.
<br><dt><code>isclass</code><dd>Return 1 for elements of <var>class</var>.
</dl>
<p>Additionally, <code>cellfun</code> accepts an arbitrary function <var>func</var>
in the form of an inline function, function handle, or the name of a
function (in a character string). In the case of a character string
argument, the function must accept a single argument named <var>x</var>, and
it must return a string value. The function can take one or more arguments,
with the inputs args given by <var>c</var>, <var>d</var>, etc. Equally the function
can return one or more output arguments. For example
<pre class="example"> cellfun (@atan2, {1, 0}, {0, 1})
⇒ans = [1.57080 0.00000]
</pre>
<p>Note that the default output argument is an array of the same size as the
input arguments.
<p>If the parameter 'UniformOutput' is set to true (the default), then the function
must return a single element which will be concatenated into the
return value. If 'UniformOutput' is false, the outputs are concatenated in
a cell array. For example
<pre class="example"> cellfun ("tolower(x)", {"Foo", "Bar", "FooBar"},
"UniformOutput",false)
⇒ ans = {"foo", "bar", "foobar"}
</pre>
<p>Given the parameter 'ErrorHandler', then <var>errfunc</var> defines a function to
call in case <var>func</var> generates an error. The form of the function is
<pre class="example"> function [...] = errfunc (<var>s</var>, ...)
</pre>
<p>where there is an additional input argument to <var>errfunc</var> relative to
<var>func</var>, given by <var>s</var>. This is a structure with the elements
'identifier', 'message' and 'index', giving respectively the error
identifier, the error message, and the index into the input arguments
of the element that caused the error. For example
<pre class="example"> function y = foo (s, x), y = NaN; endfunction
cellfun (@factorial, {-1,2},'ErrorHandler',@foo)
⇒ ans = [NaN 2]
</pre>
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<p class="noindent"><strong>See also:</strong> <a href="doc_002disempty.html#doc_002disempty">isempty</a>, <a href="doc_002dislogical.html#doc_002dislogical">islogical</a>, <a href="doc_002disreal.html#doc_002disreal">isreal</a>, <a href="doc_002dlength.html#doc_002dlength">length</a>, <a href="doc_002dndims.html#doc_002dndims">ndims</a>, <a href="doc_002dnumel.html#doc_002dnumel">numel</a>, <a href="doc_002dsize.html#doc_002dsize">size</a>.
</p></blockquote></div>
<p>An alternative is to convert the data to a different container, such as
a matrix or a data structure. Depending on the data this is possible
using the <code>cell2mat</code> and <code>cell2struct</code> functions.
<!-- ./general/cell2mat.m -->
<p><a name="doc_002dcell2mat"></a>
<div class="defun">
— Function File: <var>m</var> = <b>cell2mat</b> (<var>c</var>)<var><a name="index-cell2mat-408"></a></var><br>
<blockquote><p>Convert the cell array <var>c</var> into a matrix by concatenating all
elements of <var>c</var> into a hyperrectangle. Elements of <var>c</var> must
be numeric, logical or char, and <code>cat</code> must be able to
concatenate them together.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dmat2cell.html#doc_002dmat2cell">mat2cell</a>, <a href="doc_002dnum2cell.html#doc_002dnum2cell">num2cell</a>.
</p></blockquote></div>
<!-- ov-struct.cc -->
<p><a name="doc_002dcell2struct"></a>
<div class="defun">
— Built-in Function: <b>cell2struct</b> (<var>cell, fields, dim</var>)<var><a name="index-cell2struct-409"></a></var><br>
<blockquote><p>Convert <var>cell</var> to a structure. The number of fields in <var>fields</var>
must match the number of elements in <var>cell</var> along dimension <var>dim</var>,
that is <code>numel (</code><var>fields</var><code>) == size (</code><var>cell</var><code>, </code><var>dim</var><code>)</code>.
<pre class="example"> A = cell2struct ({'Peter', 'Hannah', 'Robert';
185, 170, 168},
{'Name','Height'}, 1);
A(1)
⇒ ans =
{
Height = 185
Name = Peter
}
</pre>
</blockquote></div>
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