How to index every field of a structure and reassign to a structure with a single element in each field

28 views (last 30 days)
I have a structure where every field is an array of the same length. I need to pass this structure on but only with a single element in each field. I thought of doing it this way
A.b = [1:10];
A.c = [2:11];
A.d = [3:12];
a = structfun(@(x) x(1),A)
but this results in
a = [1;2;3];
The answer I want for the first element is
a.b = 1;
a.c = 2;
a.d = 3;
I will want to run this in a for loop for use in the next function like this
for ii = 1:length(A.b)
...
a = structfun(@(x) x(ii),A); % but modified so that 'a' is a struct like 'A', not an array.
nextfcn(a);
...
end

Accepted Answer

KSSV
KSSV on 10 Mar 2017
A.b = [1:10];
A.c = [2:11];
A.d = [3:12];
a= A ;
for f=fieldnames(a)'
a.(f{1})(2:end)=[];
end

More Answers (2)

Chad Greene
Chad Greene on 18 Jul 2019
Alternatively, you could stick with the approach you were using, but include the 'uniformoutput',false option.
a = structfun(@(x) x(1),A,'Uni',false)

George Abrahams
George Abrahams on 30 Dec 2022
Old question, but my fieldfun function on File Exchange / GitHub does what you expected structfun to do: output a structure a with the same fields as structure A.
A = struct( 'b', 1:10, 'c', 2:11, 'd', 3:12 );
nthelement = @(n) fieldfun( @(x) x(n), A );
a = nthelement(1)
% a = struct with fields:
% b: 1
% c: 2
% d: 3
a = arrayfun( nthelement, 1:numel(A.b) )
% a = 1×10 struct array with fields:
% b
% c
% d

Categories

Find more on Structures in Help Center and File Exchange

Products

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!