File: Creating-Cell-Arrays.html

package info (click to toggle)
octave 6.2.0-1
links: PTS, VCS
area: main
in suites: bullseye
size: 124,192 kB
sloc: cpp: 322,665; ansic: 68,088; fortran: 20,980; objc: 8,121; sh: 7,719; yacc: 4,266; lex: 4,123; perl: 1,530; java: 1,366; awk: 1,257; makefile: 424; xml: 147
file content (296 lines) | stat: -rw-r--r-- 10,616 bytes
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Created by GNU Texinfo 6.7, http://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Creating Cell Arrays (GNU Octave (version 6.2.0))</title>

<meta name="description" content="Creating Cell Arrays (GNU Octave (version 6.2.0))">
<meta name="keywords" content="Creating Cell Arrays (GNU Octave (version 6.2.0))">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<link href="index.html" rel="start" title="Top">
<link href="Concept-Index.html" rel="index" title="Concept Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Cell-Arrays.html" rel="up" title="Cell Arrays">
<link href="Indexing-Cell-Arrays.html" rel="next" title="Indexing Cell Arrays">
<link href="Basic-Usage-of-Cell-Arrays.html" rel="prev" title="Basic Usage of Cell Arrays">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
kbd {font-style: oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
span.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
ul.no-bullet {list-style: none}
-->
</style>
<link rel="stylesheet" type="text/css" href="octave.css">


</head>

<body lang="en">
<span id="Creating-Cell-Arrays"></span><div class="header">
<p>
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> &nbsp; [<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>
</div>
<hr>
<span id="Creating-Cell-Arrays-1"></span><h4 class="subsection">6.3.2 Creating Cell Arrays</h4>

<p>The introductory example (see <a 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>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
</p>
<div class="example">
<pre class="example">c = cell (2,2)
     &rArr; c =

         {
           [1,1] = [](0x0)
           [2,1] = [](0x0)
           [1,2] = [](0x0)
           [2,2] = [](0x0)
         }
</pre></div>

<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
</p>
<div class="example">
<pre class="example">c1 = cell (3, 4, 5);
c2 = cell ( [3, 4, 5] );
size (c1)
     &rArr; ans =
         3   4   5
</pre></div>

<p>As can be seen, the <a 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 href="Object-Sizes.html#XREFlength">length</a>, <a href="Object-Sizes.html#XREFnumel">numel</a>,
<a href="Object-Sizes.html#XREFrows">rows</a>, and <a href="Object-Sizes.html#XREFcolumns">columns</a>.
</p>
<span id="XREFcell"></span><dl>
<dt id="index-cell">: <em></em> <strong>cell</strong> <em>(<var>n</var>)</em></dt>
<dt id="index-cell-1">: <em></em> <strong>cell</strong> <em>(<var>m</var>, <var>n</var>)</em></dt>
<dt id="index-cell-2">: <em></em> <strong>cell</strong> <em>(<var>m</var>, <var>n</var>, <var>k</var>, &hellip;)</em></dt>
<dt id="index-cell-3">: <em></em> <strong>cell</strong> <em>([<var>m</var> <var>n</var> &hellip;])</em></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>See also:</strong> <a href="Cell-Arrays-of-Strings.html#XREFcellstr">cellstr</a>, <a href="#XREFmat2cell">mat2cell</a>, <a href="#XREFnum2cell">num2cell</a>, <a 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>num2cell</code>, <code>mat2cell</code> and <code>cellslices</code> functions.
</p>
<span id="XREFnum2cell"></span><dl>
<dt id="index-num2cell">: <em><var>C</var> =</em> <strong>num2cell</strong> <em>(<var>A</var>)</em></dt>
<dt id="index-num2cell-1">: <em><var>C</var> =</em> <strong>num2cell</strong> <em>(<var>A</var>, <var>dim</var>)</em></dt>
<dd><p>Convert the numeric matrix <var>A</var> to a cell array.
</p>
<p>When no <var>dim</var> is specified, each element of <var>A</var> becomes a 1x1 element
in the output <var>C</var>.
</p>
<p>If <var>dim</var> is defined then individual elements of <var>C</var> contain all of the
elements from <var>A</var> along the specified dimension.  <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">x = [1,2;3,4]
&rArr;
    1    2
    3    4

## each element of A becomes a 1x1 element of C
num2cell (x)
   &rArr;
      {
        [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)
   &rArr;
      {
        [1,1] =
           1
           3
        [1,2] =
           2
           4
      }
## all columns (dim 2) of A appear in each element of C
num2cell (x, 2)
   &rArr;
      {
        [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])
   &rArr;
      {
        [1,1] =
           1   2
           3   4
      }
</pre></div>


<p><strong>See also:</strong> <a href="#XREFmat2cell">mat2cell</a>.
</p></dd></dl>


<span id="XREFmat2cell"></span><dl>
<dt id="index-mat2cell">: <em><var>C</var> =</em> <strong>mat2cell</strong> <em>(<var>A</var>, <var>dim1</var>, <var>dim2</var>, &hellip;, <var>dimi</var>, &hellip;, <var>dimn</var>)</em></dt>
<dt id="index-mat2cell-1">: <em><var>C</var> =</em> <strong>mat2cell</strong> <em>(<var>A</var>, <var>rowdim</var>)</em></dt>
<dd><p>Convert the matrix <var>A</var> to a cell array.
</p>
<p>Each dimension argument (<var>dim1</var>, <var>dim2</var>, etc.) is a vector of
integers which specifies how to divide that dimension&rsquo;s elements amongst the
new elements in the output <var>C</var>.  The number of elements in the <var>i</var>-th
dimension is <code>size (<var>A</var>, <var>i</var>)</code>.  Because all elements in <var>A</var>
must be partitioned, there is a requirement that <code>sum (<var>dimi</var>) == size
(<var>A</var>, i)</code>.  The size of the output cell <var>C</var> is numel (<var>dim1</var>) x
numel (<var>dim2</var>) x &hellip; x numel (<var>dimn</var>).
</p>
<p>Given a single dimensional argument, <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">x = reshape (1:12, [3, 4])'
&rArr;
    1    2    3
    4    5    6
    7    8    9
   10   11   12

</pre><pre class="example">## 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])
&rArr;
{
  [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><pre class="example">

</pre><pre class="example">## 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])
&rArr;
{
  [1,1] =

     1   2   3
     4   5   6
     7   8   9

  [2,1] =

     10   11   12
}
</pre></div>


<p><strong>See also:</strong> <a href="#XREFnum2cell">num2cell</a>, <a href="Processing-Data-in-Cell-Arrays.html#XREFcell2mat">cell2mat</a>.
</p></dd></dl>


<span id="XREFcellslices"></span><dl>
<dt id="index-cellslices">: <em><var>sl</var> =</em> <strong>cellslices</strong> <em>(<var>x</var>, <var>lb</var>, <var>ub</var>, <var>dim</var>)</em></dt>
<dd><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.
</p>
<p>In other words, it is equivalent to the following code:
</p>
<div class="example">
<pre class="example">n = length (lb);
sl = cell (1, n);
for i = 1:length (lb)
  sl{i} = x(:,&hellip;,lb(i):ub(i),&hellip;,:);
endfor
</pre></div>

<p>The position of the index is determined by <var>dim</var>.  If not specified,
slicing is done along the first non-singleton dimension.
</p>
<p><strong>See also:</strong> <a href="Processing-Data-in-Cell-Arrays.html#XREFcell2mat">cell2mat</a>, <a href="Indexing-Cell-Arrays.html#XREFcellindexmat">cellindexmat</a>, <a href="Function-Application.html#XREFcellfun">cellfun</a>.
</p></dd></dl>


<hr>
<div class="header">
<p>
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> &nbsp; [<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>
</div>



</body>
</html>