assignment of structure field values in loop - matlab - matlab

Question

I am trying to assign the field values of structure in loop.
Structure declaration with empty values:
result_struct = struct('a',{},'b',{},'c',{},'d',{})
I am assigning values in loop like that:
% assume a, b, c, d are variables in my workspace
% field names match with the variable names
for index=1:n
% some computation and store results in variables (a-d)
result_struct(index).a = a;
result_struct(index).b = b;
result_struct(index).c = c;
result_struct(index).d = d;
end
How can I assign the values to the fields using another loop? Like that:
for fname = fieldnames(result_struct)'
result_struct(index).fname = fname; % field names and variable names match
end

Answer 1

You need to use dynamic field names to assign to the struct (the leff-hand side). For the right hand side you could use eval but that is dangerous, so it's better to save your variable fname to a file and then load it back in as a struct prior to accessing fname, again using dynamic field names.
names = fieldnames(result_struct);
for k = 1:numel(names)
% Save variable to a file
save('tmp.mat', names{k});
% Load it back into a struct
tmp = load('tmp.mat', names{k});
result_struct(index).(names{k}) = tmp.(names{k});
end
Alternately, you can use the save and load to just transform the entire thing into a struct without having to loop through the fields.
fields = fieldnames(result_struct);
% Save all relevant variables to a file
save('tmp.mat', fields{:});
% Load it back into the result_struct
result_struct(index) = orderfields(load('tmp.mat'), fields);