<html lang="en"> <head> <title>Structure Arrays - GNU Octave</title> <meta http-equiv="Content-Type" content="text/html"> <meta name="description" content="GNU Octave"> <meta name="generator" content="makeinfo 4.13"> <link title="Top" rel="start" href="index.html#Top"> <link rel="up" href="Structures.html#Structures" title="Structures"> <link rel="prev" href="Basic-Usage-and-Examples.html#Basic-Usage-and-Examples" title="Basic Usage and Examples"> <link rel="next" href="Creating-Structures.html#Creating-Structures" title="Creating Structures"> <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> <meta http-equiv="Content-Style-Type" content="text/css"> <style type="text/css"><!-- pre.display { font-family:inherit } pre.format { font-family:inherit } pre.smalldisplay { font-family:inherit; font-size:smaller } pre.smallformat { font-family:inherit; font-size:smaller } pre.smallexample { font-size:smaller } pre.smalllisp { font-size:smaller } span.sc { font-variant:small-caps } span.roman { font-family:serif; font-weight:normal; } span.sansserif { font-family:sans-serif; font-weight:normal; } --></style> </head> <body> <div class="node"> <a name="Structure-Arrays"></a> <p> Next: <a rel="next" accesskey="n" href="Creating-Structures.html#Creating-Structures">Creating Structures</a>, Previous: <a rel="previous" accesskey="p" href="Basic-Usage-and-Examples.html#Basic-Usage-and-Examples">Basic Usage and Examples</a>, Up: <a rel="up" accesskey="u" href="Structures.html#Structures">Structures</a> <hr> </div> <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 <pre class="example"> x(1).a = "string1"; x(2).a = "string2"; x(1).b = 1; x(2).b = 2; </pre> <p class="noindent">which creates a 2-by-1 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: <pre class="example"> x ⇒ x = { 1x2 struct array containing the fields: a b } </pre> <p>Individual elements of the structure array can be returned by indexing the variable like <var>x</var><code>(1)</code>, which returns a structure with two fields: <pre class="example"> x(1) ⇒ ans = { a = string1 b = 1 } </pre> <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: <pre class="example"> x.a ⇒ ans = string1 ans = string2 </pre> <p>Here is another example, using this comma separated list on the left-hand side of an assignment: <pre class="example"> [x.a] = deal("new string1", "new string2"); x(1).a ⇒ ans = new string1 x(2).a ⇒ ans = new string2 </pre> <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>): <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> <p>The function <code>size</code> will return the size of the structure. For the example above <pre class="example"> size(x) ⇒ ans = 1 4 </pre> <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 <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> </body></html>