How can I access all values of a field in an array of nested structs
17 views (last 30 days)
Show older comments
The following code creates an array of nested structs (length = 4).
nested_struct = struct(...
'a', 1, ...
'b', 1 ...
);
s = struct( ...
'c', 0, ...
'nested', nested_struct ...
);
array_of_nested_struct = repmat(s, 4, 1);
How can I easily access an array of all of the values of the field a ?
For example, I'd like to compute the sum as
% sum(array_of_nested_struct.nested.a)
However, this does not work because
array_of_nested_struct.nested
does not produce a struct array.
My only solution seems overly cumbersome, and requries usage of intermediate variables:
% The following is not an array of structures
array_of_nested_struct.nested;
% So convert it into a struct array
nested = [array_of_nested_struct.nested];
% Do the same for the next level
a_value_array = [nested.a];
% Finally compute sum
sum(a_value_array)
is there a better syntax to achieve this result? The syntax should also support code generation without any data copies
Thanks!
2 Comments
Stephen23
on 7 Aug 2023
"is there a better syntax to achieve this result?"
Don't spread data over lots of different structures if it is intended to be processed together.
Answers (1)
Benjamin
on 7 Aug 2023
Edited: Benjamin
on 7 Aug 2023
% Given code to create the array_of_nested_struct
nested_struct = struct(...
'a', 1, ...
'b', 1 ...
);
s = struct( ...
'c', 0, ...
'nested', nested_struct ...
);
array_of_nested_struct = repmat(s, 4, 1);
% Use arrayfun to extract 'a' field values and compute the sum directly
sum_a_values = sum(arrayfun(@(x) x.nested.a, array_of_nested_struct));
% Display the sum
disp("Sum of 'a' values: " + sum_a_values);
So this here will give you the array:
array = arrayfun(@(x) x.nested.a, array_of_nested_struct)
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!