How do I preallocate memory for a structure in MATLAB 7.6 (R2008a)?
3 views (last 30 days)
Show older comments
MathWorks Support Team
on 23 Sep 2013
Edited: MathWorks Support Team
on 13 Dec 2021
I would like to know how to preallocate memory for a structure.
Accepted Answer
MathWorks Support Team
on 10 Dec 2021
Edited: MathWorks Support Team
on 13 Dec 2021
There is a way to preallocate memory for a structure in MATLAB 7.6 (R2008a) using the STRUCT and REPMAT commands.
EXAMPLE 1: A structure with two fields
s.field1
s.field2
field_names = {'field1','field2'}; % Cell with field names
empty_cells = repmat(cell(1),1,numel(field_names));
entries = {field_names{:} ; empty_cells{:}};
s = struct(entries{:});
EXAMPLE 2: A structure with a field with a subfield
s.field1.subfield
s = struct('field1',struct('subfield',cell(1)));
EXAMPLE 3: An array of structures
v(1).field1
...
v(100).field1
s = struct('field1',cell(1));
v = repmat(s,100,1);
Even though the data elements pointed to by the different fields in a structure are not stored contiguously, a benefit of preallocating structures is that you avoid the (possibly time-consuming) operation of dynamically growing the structure field header. Please refer to the following documentation page for more information:
1 Comment
Walter Roberson
on 15 Feb 2017
The line
empty_cells = repmat(cell(1),1,numel(field_names));
creates a cell array of copies of [] . The line
entries = {field_names{:} ; empty_cells{:}};
arranges those copies below the field names, like
{ 'first', 'second', 'third';
[], [], [] }
and the line
s = struct(entries{:});
converts that to
a = struct('first', [], 'second', [], 'third', [])
so already [] is being used.
The code given in the first part of the solution is code to automatically generate this just given the field names.
More Answers (0)
See Also
Categories
Find more on Structures in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!