Documentation

Access Data in Nested Structures

This example shows how to index into a structure that is nested within another structure. The general syntax for accessing data in a particular field is

structName(index).nestedStructName(index).fieldName(indices)

When a structure is scalar (1-by-1), you do not need to include the indices to refer to the single element. For example, create a scalar structure s, where field n is a nested scalar structure with fields a, b, and c:

s.n.a = ones(3);
s.n.b = eye(4);
s.n.c = magic(5);

Access the third row of field b:

third_row_b = s.n.b(3,:)

Variable third_row_b contains the third row of eye(4).

third_row_b =
0     0     1     0

Expand s so that both s and n are nonscalar (1-by-2):

s(1).n(2).a = 2*ones(3);
s(1).n(2).b = 2*eye(4);
s(1).n(2).c = 2*magic(5);

s(2).n(1).a = '1a';
s(2).n(2).a = '2a';
s(2).n(1).b = '1b';
s(2).n(2).b = '2b';
s(2).n(1).c = '1c';
s(2).n(2).c = '2c';

Structure s now contains the data shown in the following figure. Access part of the array in field b of the second element in n within the first element of s:

part_two_eye = s(1).n(2).b(1:2,1:2)

This returns the 2-by-2 upper left corner of 2*eye(4):

part_two_eye =
2     0
0     2