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6.1.2 Structure Arrays

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

x(1).a = "string1";
x(2).a = "string2";
x(1).b = 1;
x(2).b = 2;

which creates a 1-by-2 structure array with two fields. Another way to create a structure array is with the struct function (see Creating Structures). As previously, to print the value of the structure array, you can type its name:

x
⇒ x =
{
1x2 struct array containing the fields:

a
b
}

Individual elements of the structure array can be returned by indexing the variable like x(1), which returns a structure with two fields:

x(1)
⇒ ans =
{
a = string1
b =  1
}

Furthermore, the structure array can return a comma separated list of field values (see Comma Separated Lists), if indexed by one of its own field names. For example:

x.a
⇒
ans = string1
ans = string2

Here is another example, using this comma separated list on the left-hand side of an assignment:

[x.a] = deal ("new string1", "new string2");
x(1).a
⇒ ans = new string1
x(2).a
⇒ ans = new string2

Just as for numerical arrays, it is possible to use vectors as indices (see Index Expressions):

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

The function size will return the size of the structure. For the example above

size (x)
⇒ ans =

1   4

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

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

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