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Matlab: how to sum fields of two equivalent structures?

I am working in Matlab. I have defined:

a(1).x=1;
a(1).y=2;
a(1).z.w=3;

a(2).x=4;
a(2).y=5;
a(2).z.w=6;

Now I am trying to add fields to two structures a (1) and a (2) such that I get:

c.x = 5; 
c.y = 7; 
c.z.w = 9;

Any idea how I can do this in an elegant way? Note that in the original problem, the structures have many more fields (about 50).

Thank you in advance! Jose

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3 answers


Here is a solution for any depth of structure

Script command code (or MATLAB)

a(1).x=1;
a(1).y=2;
a(1).z.w=3;

a(2).x=4;
a(2).y=5;
a(2).z.w=6;
c=a(1);
c = returnStruct(c, a(2));
%{
you can also sum any amount of structs
for i=2:length(a)
   c=returnStruct(c, a(i));
end
%}

with recursive function



function rs = returnStruct(s,a)
fn = fieldnames(s);
for i=1:length(fn)
  if isstruct(s.(fn{i}))
    s.(fn{i}) = returnStruct(s.(fn{i}), a.(fn{i}));
  else
    s.(fn{i}) = s.(fn{i})+a.(fn{i});
  end
end
rs = s;
end

I tested it for deeper levels of structures and it worked great. Maybe you need to adjust it a little to your case, but this should be the way to go.

Unfortunately, any type function struct2cell

only converts the first level, so you need something else.

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If the deepest level of the substructure is 2, then this code will work:



fields=fieldnames(a);
for i=1:numel(fields)
if isstruct(a(1).(fields{i}))
fields2=fieldnames(a(1).(fields{i}));
for j=1:numel(fields2)
a(3).(fields{i}).(fields2{j})= a(1).(fields{i}).(fields2{j})+a(2).(fields{i}).(fields2{j});
end
else
a(3).(fields{i})=a(1).(fields{i})+a(2).(fields{i});
end
end
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You can have a simple recursive solution

function r = sumfields(s)
if isstruct(s)
    for f = fieldnames(s).'
        r.(f{1}) = sumfields([s.(f{1})]);
    end
else
    r = sum(s);
end
end
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