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<h4 class="subsection">6.1.4 Manipulating Structures</h4>
<p>Other functions that can manipulate the fields of a structure are given below.
<!-- nfields src/ov-struct.cc -->
<p><a name="doc_002dnfields"></a>
<div class="defun">
— Built-in Function: <b>nfields</b> (<var>s</var>)<var><a name="index-nfields-444"></a></var><br>
<blockquote><p>Return the number of fields of the structure <var>s</var>.
</p></blockquote></div>
<!-- fieldnames src/ov-struct.cc -->
<p><a name="doc_002dfieldnames"></a>
<div class="defun">
— Built-in Function: <b>fieldnames</b> (<var>struct</var>)<var><a name="index-fieldnames-445"></a></var><br>
<blockquote><p>Return a cell array of strings naming the elements of the structure
<var>struct</var>. It is an error to call <code>fieldnames</code> with an
argument that is not a structure.
</p></blockquote></div>
<!-- isfield src/ov-struct.cc -->
<p><a name="doc_002disfield"></a>
<div class="defun">
— Built-in Function: <b>isfield</b> (<var>x, name</var>)<var><a name="index-isfield-446"></a></var><br>
<blockquote><p>Return true if the <var>x</var> is a structure and it
includes an element named <var>name</var>. If <var>name</var> is a cell
array of strings then a logical array of equal dimension is returned.
</p></blockquote></div>
<!-- getfield scripts/miscellaneous/getfield.m -->
<p><a name="doc_002dgetfield"></a>
<div class="defun">
— Function File: [<var>v1</var>, <small class="dots">...</small>] = <b>getfield</b> (<var>s, key, <small class="dots">...</small></var>)<var><a name="index-getfield-447"></a></var><br>
<blockquote><p>Extract a field from a structure (or a nested structure). For example:
<pre class="example"> ss(1,2).fd(3).b = 5;
getfield (ss, {1,2}, "fd", {3}, "b")
⇒ 5
</pre>
<p>Note that the function call in the previous example is equivalent to
the expression
<pre class="example"> i1 = {1,2}; i2 = "fd"; i3 = {3}; i4= "b";
ss(i1{:}).(i2)(i3{:}).(i4)
⇒ 5
</pre>
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dsetfield.html#doc_002dsetfield">setfield</a>, <a href="doc_002drmfield.html#doc_002drmfield">rmfield</a>, <a href="doc_002disfield.html#doc_002disfield">isfield</a>, <a href="doc_002disstruct.html#doc_002disstruct">isstruct</a>, <a href="doc_002dfieldnames.html#doc_002dfieldnames">fieldnames</a>, <a href="doc_002dstruct.html#doc_002dstruct">struct</a>.
</p></blockquote></div>
<!-- setfield scripts/miscellaneous/setfield.m -->
<p><a name="doc_002dsetfield"></a>
<div class="defun">
— Function File: [<var>k1</var>, <small class="dots">...</small>, <var>v1</var>] = <b>setfield</b> (<var>s, k1, v1, <small class="dots">...</small></var>)<var><a name="index-setfield-448"></a></var><br>
<blockquote><p>Set a field member in a (nested) structure array. For example:
<pre class="example"> oo(1,1).f0 = 1;
oo = setfield (oo, {1,2}, "fd", {3}, "b", 6);
oo(1,2).fd(3).b == 6
⇒ ans = 1
</pre>
<p>Note that the same result as in the above example could be achieved by:
<pre class="example"> i1 = {1,2}; i2 = "fd"; i3 = {3}; i4 = "b";
oo(i1{:}).(i2)(i3{:}).(i4) == 6
⇒ ans = 1
</pre>
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dgetfield.html#doc_002dgetfield">getfield</a>, <a href="doc_002drmfield.html#doc_002drmfield">rmfield</a>, <a href="doc_002disfield.html#doc_002disfield">isfield</a>, <a href="doc_002disstruct.html#doc_002disstruct">isstruct</a>, <a href="doc_002dfieldnames.html#doc_002dfieldnames">fieldnames</a>, <a href="doc_002dstruct.html#doc_002dstruct">struct</a>.
</p></blockquote></div>
<!-- rmfield src/ov-struct.cc -->
<p><a name="doc_002drmfield"></a>
<div class="defun">
— Built-in Function: <b>rmfield</b> (<var>s, f</var>)<var><a name="index-rmfield-449"></a></var><br>
<blockquote><p>Return a copy of the structure (array) <var>s</var> with the field <var>f</var>
removed. If <var>f</var> is a cell array of strings or a character array, remove
the named fields.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dcellstr.html#doc_002dcellstr">cellstr</a>, <a href="doc_002discellstr.html#doc_002discellstr">iscellstr</a>, <a href="doc_002dsetfield.html#doc_002dsetfield">setfield</a>.
</p></blockquote></div>
<!-- orderfields scripts/miscellaneous/orderfields.m -->
<p><a name="doc_002dorderfields"></a>
<div class="defun">
— Function File: [<var>t</var>, <var>p</var>] = <b>orderfields</b> (<var>s1</var>)<var><a name="index-orderfields-450"></a></var><br>
— Function File: [<var>t</var>, <var>p</var>] = <b>orderfields</b> (<var>s1, s2</var>)<var><a name="index-orderfields-451"></a></var><br>
<blockquote><p>Return a copy of <var>s1</var> with fields arranged alphabetically or
as specified by <var>s2</var>.
<p>Given one struct, arrange field names in <var>s1</var> alphabetically.
<p>If the second argument is a struct, arrange field names in <var>s1</var>
as they appear in <var>s2</var>. The second argument may also specify the
order in a permutation vector or a cell array of strings containing
the fieldnames of <var>s1</var> in the desired order.
<p>The optional second output argument <var>p</var> is assigned the permutation
vector
which converts the original name order into the new name order.
<p>Examples:
<pre class="example"> s = struct("d", 4, "b", 2, "a", 1, "c", 3);
t1 = orderfields (s)
⇒ t1 =
{
a = 1
b = 2
c = 3
d = 4
}
t = struct("d", {}, "c", {}, "b", "a", {});
t2 = orderfields (s, t)
⇒ t2 =
{
d = 4
c = 3
b = 2
a = 1
}
t3 = orderfields (s, [3, 2, 4, 1]);
⇒ t3 =
{
a = 1
b = 2
c = 3
d = 4
}
[t4, p] = orderfields (s, {"d", "c", "b", "a"})
⇒ t4 =
{
d = 4
c = 3
b = 2
a = 1
}
p =
1
4
2
3
</pre>
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dgetfield.html#doc_002dgetfield">getfield</a>, <a href="doc_002drmfield.html#doc_002drmfield">rmfield</a>, <a href="doc_002disfield.html#doc_002disfield">isfield</a>, <a href="doc_002disstruct.html#doc_002disstruct">isstruct</a>, <a href="doc_002dfieldnames.html#doc_002dfieldnames">fieldnames</a>, <a href="doc_002dstruct.html#doc_002dstruct">struct</a>.
</p></blockquote></div>
<!-- substruct scripts/miscellaneous/substruct.m -->
<p><a name="doc_002dsubstruct"></a>
<div class="defun">
— Function File: <b>substruct</b> (<var>type, subs, <small class="dots">...</small></var>)<var><a name="index-substruct-452"></a></var><br>
<blockquote><p>Create a subscript structure for use with <code>subsref</code> or
<code>subsasgn</code>. For example:
<pre class="example"> idx = substruct ("()", {3, ":"})
⇒
idx =
{
type = ()
subs =
{
[1,1] = 3
[1,2] = :
}
}
x = [1, 2, 3; 4, 5, 6; 7, 8, 9];
subsref (x, idx)
⇒ 7 8 9
</pre>
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dsubsref.html#doc_002dsubsref">subsref</a>, <a href="doc_002dsubsasgn.html#doc_002dsubsasgn">subsasgn</a>.
</p></blockquote></div>
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