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<a name="Structure-Arrays"></a>
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<a name="Structure-Arrays-1"></a>
<h4 class="subsection">6.1.2 Structure Arrays</h4>
<p>A structure array is a particular instance of a structure, where each of
the fields of the structure is represented by a cell array. Each of
these cell arrays has the same dimensions. Conceptually, a structure
array can also be seen as an array of structures with identical
fields. An example of the creation of a structure array is
</p>
<div class="example">
<pre class="example">x(1).a = "string1";
x(2).a = "string2";
x(1).b = 1;
x(2).b = 2;
</pre></div>
<p>which creates a 1-by-2 structure array with two fields. Another way
to create a structure array is with the <code>struct</code> function
(see <a href="Creating-Structures.html#Creating-Structures">Creating Structures</a>). As previously, to print the value of
the structure array, you can type its name:
</p>
<div class="example">
<pre class="example">x
⇒ x =
{
1x2 struct array containing the fields:
a
b
}
</pre></div>
<p>Individual elements of the structure array can be returned by indexing
the variable like <code><var>x</var>(1)</code>, which returns a structure with
two fields:
</p>
<div class="example">
<pre class="example">x(1)
⇒ ans =
{
a = string1
b = 1
}
</pre></div>
<p>Furthermore, the structure array can return a comma separated list of
field values (see <a href="Comma-Separated-Lists.html#Comma-Separated-Lists">Comma Separated Lists</a>), if indexed by one of its
own field names. For example:
</p>
<div class="example">
<pre class="example">x.a
⇒
ans = string1
ans = string2
</pre></div>
<p>Here is another example, using this comma separated list on the
left-hand side of an assignment:
</p>
<div class="example">
<pre class="example">[x.a] = deal ("new string1", "new string2");
x(1).a
⇒ ans = new string1
x(2).a
⇒ ans = new string2
</pre></div>
<p>Just as for numerical arrays, it is possible to use vectors as indices
(see <a href="Index-Expressions.html#Index-Expressions">Index Expressions</a>):
</p>
<div class="example">
<pre class="example">x(3:4) = x(1:2);
[x([1,3]).a] = deal ("other string1", "other string2");
x.a
⇒
ans = other string1
ans = new string2
ans = other string2
ans = new string2
</pre></div>
<p>The function <code>size</code> will return the size of the structure. For
the example above
</p>
<div class="example">
<pre class="example">size (x)
⇒ ans =
1 4
</pre></div>
<p>Elements can be deleted from a structure array in a similar manner to a
numerical array, by assigning the elements to an empty matrix. For
example
</p>
<div class="example">
<pre class="example">in = struct ("call1", {x, Inf, "last"},
"call2", {x, Inf, "first"})
⇒ in =
{
1x3 struct array containing the fields:
call1
call2
}
in(1) = [];
in.call1
⇒
ans = Inf
ans = last
</pre></div>
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