Octave Programming Tutorial/Struct Arrays

A structure in Octave groups different data types called fields in a single object. Fields are accessed by their names.

Declaring a structure
A structure is declared by assigning values to its fields. A period (.) separates the name of the field and the name of the structure:

>> city.name = 'Liege'; >> city.country = 'Belgium'; >> city.longitude = 50.6333; >> city.latitude = 5.5666;

The fields of a structure and their value can by displayed by simply entering the name of the struct:

>> city city = {  name = Liege country = Belgium longitude = 50.633 latitude = 5.5666 }

Manipulating structures
A structure can be copied as any objects:

>> city_copy = city;

In most circumstance, the fields of a structure can be manipulated with the period operator. The value of a field can be overwritten by:

>> city.name = 'Outremeuse';

In the same way, the value of a field can be retrieved by:

>> city.name ans = Outremeuse

The function isstruct can be used to test if object is a structure or not. With the function fieldnames all field names are returned as a cell array:

>> fieldnames(city) ans = {  [1,1] = name [2,1] = country [3,1] = longitude [4,1] = latitude }

To test if a structure contains the a given field named, the function isfield can be used:

>> isfield(city,'name') ans = 1

The value of a field can be extract with getfield:

>> getfield(city,'name') ans = Liege

In a similar way, the value of a field can be set with setfield:

>> setfield(city,'name','Outremeuse')

The functions isfield, getfield and setfield are useful when the names of a structure are determined during execution of the program.