MATLAB Answers

How do I preallocate memory for a structure in MATLAB 7.6 (R2008a)?

23 views (last 30 days)
I would like to know how to preallocate memory for a structure.

Accepted Answer

MathWorks Support Team
MathWorks Support Team on 23 Sep 2013
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
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 = struct('field1',struct('subfield',cell(1)));
EXAMPLE 3: An array of structures
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:


Pooja Mehta
Pooja Mehta on 15 Feb 2017
for command
empty_cells = repmat(cell(1),1,numel(field_names));
can't we use [], for defining empty cells under field_name, like
filed_name = {'field1',[],'field2',[]};
Walter Roberson
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.

Sign in to comment.

More Answers (0)

Sign in to answer this question.