Next: Creating Structures, Up: Data Structures
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. 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 2-by-1 structure array with two fields. As previously, to print the value of the structure array, you can type its name:
octave:1> 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 the
two fields like
octave:2> x(1)
ans =
{
a = string1
b = 1
}
Furthermore, the structure array can return a comma separated list (see Comma Separated Lists), if indexed by one of its own field names. For example
octave:3> x.a
ans = string1
ans = string2
Here is another example, using this comma separated list on the left-hand side of an assignment:
octave:4> [x.a] = deal("new string1", "new string2");
octave:5> x(1).a
ans = new string1
octave:6> x(2).a
ans = new string2
Just as for numerical arrays, it is possible to use vectors as indices (see Index Expressions):
octave:7> x(3:4) = x(1:2);
octave:8> [x([1,3]).a] = deal("other string1", "other string2");
octave:9> 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
octave:10> 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 (1, :) = []
in =
{
call1 =
(,
[1] = Inf
[2] = last
,)
call2 =
(,
[1] = Inf
[2] = first
,)
}